Interplay between subpictures and in-loop filtering

ABSTRACT

An example method of video processing includes: determining, for a conversion between a chroma block of a current processing unit of a current subpicture of a current picture of a video and a bitstream of the video, that a cross component adaptive loop filtering operation is applied to the chroma block, wherein the current picture comprises one or more subpictures; and performing the conversion based on the determining, wherein in the cross component adaptive loop filtering operation, a chroma sample of the chroma block is filtered based on information of luma samples, and wherein one or more luma samples located outside the current processing unit are excluded from the filtering of the chroma sample.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.17/723,175, filed on Apr. 18, 2022, which is a continuation ofInternational Patent Application No. PCT/CN2020/121768, filed on Oct.19, 2020, which claims the priority to and benefits of InternationalPatent Application No. PCT/CN2019/111807, filed on Oct. 18, 2019. Theentire disclosure of the aforementioned applications is incorporated byreference as part of the disclosure of this application.

TECHNICAL FIELD

This document is related to video and image coding and decodingtechnologies.

BACKGROUND

Digital video accounts for the largest bandwidth use on the internet andother digital communication networks. As the number of connected userdevices capable of receiving and displaying video increases, it isexpected that the bandwidth demand for digital video usage will continueto grow.

SUMMARY

The disclosed techniques may be used by video or image decoder orencoder embodiments for in which sub-picture based coding or decoding isperformed.

In one example aspect a method of video processing is disclosed. Themethod includes performing a conversion between a picture of a video anda bitstream representation of the video. The picture comprises one ormore sub-pictures, and the bitstream representation conforms to a formatrule that specifies that a length of a syntax element is equal toCeil(Log 2(SS)) bits. SS is greater than 0, and the syntax elementindicating a horizontal or a vertical position of a top-left corner of acoding tree unit of a sub-picture of the picture.

In another example aspect a method of video processing is disclosed. Themethod includes performing a conversion between a picture of a video anda bitstream representation of the video, wherein the picture comprisesone or more sub-pictures. The bitstream representation conforms to aformat rule that specifies that different sub-pictures have differentidentifiers.

In another example aspect a method of video processing is disclosed. Themethod includes determining, for a video block in a first video regionof a video, whether a position at which a temporal motion vectorpredictor is determined for a conversion between the video block and abitstream representation of the current video block using an affine modeis within a second video region; and performing the conversion based onthe determining.

In another example aspect, another method of video processing isdisclosed. The method includes determining, for a video block in a firstvideo region of a video, whether a position at which an integer samplein a reference picture is fetched for a conversion between the videoblock and a bitstream representation of the current video block iswithin a second video region, wherein the reference picture is not usedin an interpolation process during the conversion; and performing theconversion based on the determining.

In another example aspect, another method of video processing isdisclosed. The method includes determining, for a video block in a firstvideo region of a video, whether a position at which a reconstructedluma sample value is fetched for a conversion between the video blockand a bitstream representation of the current video block is within asecond video region; and performing the conversion based on thedetermining.

In another example aspect, another method of video processing isdisclosed. The method includes determining, for a video block in a firstvideo region of a video, whether a position at which a check regardingsplitting, depth derivation or split flag signaling for the video blockis performed during a conversion between the video block and a bitstreamrepresentation of the current video block is within a second videoregion; and performing the conversion based on the determining.

In another example aspect, another method of video processing isdisclosed. The method includes performing a conversion between a videocomprising one or more video pictures comprising one or more videoblocks, and a coded representation of the video, wherein the codedrepresentation complies with a coding syntax requirement that theconversion is not to use sub-picture coding/decoding and a dynamicresolution conversion coding/decoding tool or a reference pictureresampling tool within a video unit.

In another example aspect, another method of video processing isdisclosed. The method includes performing a conversion between a videocomprising one or more video pictures comprising one or more videoblocks, and a coded representation of the video, wherein the codedrepresentation complies with a coding syntax requirement that a firstsyntax element subpic_grid_idx[i][j] is not larger than a second syntaxelement max_subpics_minus1.

In yet another example aspect, the above-described method may beimplemented by a video encoder apparatus that comprises a processor.

In yet another example aspect, the above-described method may beimplemented by a video decoder apparatus that comprises a processor.

In yet another example aspect, these methods may be embodied in the formof processor-executable instructions and stored on a computer-readableprogram medium.

These, and other, aspects are further described in the present document.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of region constraint in temporal motion vectorprediction (TMVP) and sub-block TMVP.

FIG. 2 shows an example of a hierarchical motion estimation scheme.

FIG. 3 is a block diagram of an example of a hardware platform used forimplementing techniques described in the present document.

FIG. 4 is a flowchart for an example method of video processing.

FIG. 5 shows an example of a picture with 18 by 12 luma coding treeunits (CTUs) that is partitioned into 12 tiles and 3 raster-scan slices(informative).

FIG. 6 shows an example of picture with 18 by 12 luma CTUs that ispartitioned into 24 tiles and 9 rectangular slices (informative).

FIG. 7 shows an example of a picture that is partitioned into 4 tiles,11 bricks, and 4 rectangular slices (informative).

FIG. 8 is a block diagram showing an example video processing system inwhich various techniques disclosed herein may be implemented.

FIG. 9 is a block diagram that illustrates an example video codingsystem.

FIG. 10 is a block diagram that illustrates an encoder in accordancewith some embodiments of the present disclosure.

FIG. 11 is a block diagram that illustrates a decoder in accordance withsome embodiments of the present disclosure.

FIG. 12 is a flowchart representation of a method for video processingin accordance with the present technology.

FIG. 13 is a flowchart representation of another method for videoprocessing in accordance with the present technology.

FIG. 14 is a flowchart representation of another method for videoprocessing in accordance with the present technology.

FIG. 15 is a flowchart representation of another method for videoprocessing in accordance with the present technology.

FIG. 16 is a flowchart representation of another method for videoprocessing in accordance with the present technology.

FIG. 17 is a flowchart representation of another method for videoprocessing in accordance with the present technology.

FIG. 18 is a flowchart representation of another method for videoprocessing in accordance with the present technology.

FIG. 19 is a flowchart representation of yet another method for videoprocessing in accordance with the present technology.

DETAILED DESCRIPTION

The present document provides various techniques that can be used by adecoder of image or video bitstreams to improve the quality ofdecompressed or decoded digital video or images. For brevity, the term“video” is used herein to include both a sequence of pictures(traditionally called video) and individual images. Furthermore, a videoencoder may also implement these techniques during the process ofencoding in order to reconstruct decoded frames used for furtherencoding.

Section headings are used in the present document for ease ofunderstanding and do not limit the embodiments and techniques to thecorresponding sections. As such, embodiments from one section can becombined with embodiments from other sections.

1. Summary

This document is related to video coding technologies. Specifically, itis related to palette coding with employing base colors basedrepresentation in video coding. It may be applied to the existing videocoding standard like High Efficiency Video Coding (HEVC), or thestandard (e.g., Versatile Video Coding (VVC)) to be finalized. It may bealso applicable to future video coding standards or video codec.

2. Initial Discussion

Video coding standards have evolved primarily through the development ofthe well-known International Telecommunication Union-TelecommunicationStandardization Sector (ITU-T) and International Organization forStandardization (ISO)/International Electrotechnical Commission (IEC)standards. The ITU-T produced H.261 and H.263, ISO/IEC produced MovingPicture Experts Group (MPEG)-1 and MPEG-4 Visual, and the twoorganizations jointly produced the H.262/MPEG-2 Video and H.264/MPEG-4Advanced Video Coding (AVC) and H.265/HEVC standards [1,2]. Since H.262,the video coding standards are based on the hybrid video codingstructure wherein temporal prediction plus transform coding areutilized. To explore the future video coding technologies beyond HEVC,Joint Video Exploration Team (JVET) was founded by Video Coding ExpertsGroup (VCEG) and MPEG jointly in 2015. Since then, many new methods havebeen adopted by JVET and put into the reference software named JointExploration Model (JEM). In April 2018, the Joint Video Expert Team(JVET) between VCEG (Q6/16) and ISO/IEC Joint technical committee (JTC)1sub-committee (SC)29/working group (WG)11 (MPEG) was created to work onthe VVC standard targeting at 50% bitrate reduction compared to HEVC.

2.1 The Region Constraint in TMVP and Sub-Block TMVP in VVC

FIG. 1 illustrates example region constraint in TMVP and sub-block TMVP.In TMVP and sub-block TMVP, it is constrained that a temporal motionvector (MV) can only be fetched from the collocated CTU plus a column of4×4 blocks as shown in FIG. 1 .

2.2 Example Sub-Picture

In some embodiments, sub-picture-based coding techniques based onflexible tiling approach can be implemented. Summary of thesub-picture-based coding techniques includes the following:

-   -   (1) Pictures can be divided into sub-pictures.    -   (2) The indication of existence of sub-pictures is indicated in        the sequence parameter set (SPS), along with other        sequence-level information of sub-pictures.    -   (3) Whether a sub-picture is treated as a picture in the        decoding process (excluding in-loop filtering operations) can be        controlled by the bitstream.    -   (4) Whether in-loop filtering across sub-picture boundaries is        disabled can be controlled by the bitstream for each        sub-picture. The deblocking filter (DBF), SAO, and ALF processes        are updated for controlling of in-loop filtering operations        across sub-picture boundaries.    -   (5) For simplicity, as a starting point, the sub-picture width,        height, horizontal offset, and vertical offset are signalled in        units of luma samples in SPS. Sub-picture boundaries are        constrained to be slice boundaries.    -   (6) Treating a sub-picture as a picture in the decoding process        (excluding in-loop filtering operations) is specified by        slightly updating the coding_tree_unit( ) syntax, and updates to        the following decoding processes:        -   The derivation process for (advanced) temporal luma motion            vector prediction        -   The luma sample bilinear interpolation process        -   The luma sample 8-tap interpolation filtering process        -   The chroma sample interpolation process    -   (7) Sub-picture IDs are explicitly specified in the SPS and        included in the tile group headers to enable extraction of        sub-picture sequences without the need of changing video coding        layer (VCL) network abstraction layer (NAL) units.    -   (8) Output sub-picture sets (OSPS) are proposed to specify        normative extraction and conformance points for sub-pictures and        sets thereof.

2.3 Example Sub-Pictures in Versatile Video Coding Sequence ParameterSet RBSP Syntax

Descriptor seq_parameter_set_rbsp( ) {  sps_decoding_parameter_set_idu(4)  sps_video_parameter_set_id u(4) . . . pic_width_max_in_luma_samples ue(v)  pic_height_max_in_luma_samplesue(v)  subpics_present_flag u(1)  if( subpics_present_flag ) {  max_subpics_minus1 u(8)   subpic_grid_col_width_minus1 u(v)  subpic_grid_row_height_minus1 u(v)   for( i = 0; i <NumSubPicGridRows; i++ )    for( j = 0; j < NumSubPicGridCols; j++ )    subpic_grid_idx[ i ][ j ] u(v)   for( i = 0; i <= NumSubPics; i++ ){    subpic_treated_as_pic_flag[ i ] u(1)   loop_filter_across_subpic_enabled_flag [ i ] u(1)   }  } . . . }subpics_present_flag equal to 1 indicates that sub-picture parametersare present in the present in the SPS raw byte sequence payload (RBSP)syntax. subpics_present_flag equal to 0 indicates that sub-pictureparameters are not present in the present in the SPS RBSP syntax.

-   -   NOTE 2—When a bitstream is the result of a sub-bitstream        extraction process and contains only a subset of the        sub-pictures of the input bitstream to the sub-bitstream        extraction process, it might be required to set the value of        subpics_present_flag equal to 1 in the RBSP of the SPSs.        max_subpics_minus1 plus 1 specifies the maximum number of        sub-pictures that may be present in the coded video sequence        (CVS). max_subpics_minus1 shall be in the range of 0 to 254. The        value of 255 is reserved for future use by ITU-T ISO/IEC.        subpic_grid_col_width_minus1 plus 1 specifies the width of each        element of the sub-picture identifier grid in units of 4        samples. The length of the syntax element is Ceil(Log        2(pic_width_max_in_luma_samples/4)) bits. The variable        NumSubPicGridCols is derived as follows:

NumSubPicGridCols=(pic_width_max_in_luma_samples+subpic_grid_col_width_minus1*4+3)/(subpic_grid_col_width_minus1*4+4)  (7-5)

subpic_grid_row_height_minus1 plus 1 specifies the height of eachelement of the sub-picture identifier grid in units of 4 samples. Thelength of the syntax element is Ceil(Log2(pic_height_max_in_luma_samples/4)) bits. The variableNumSubPicGridRows is derived as follows:

NumSubPicGridRows=(pic_height_max_in_luma_samples+subpic_grid_row_height_minus1*4+3)/(subpic_grid_row_height_minus1*4+4)  (7-6)

subpic_grid_idx[i][j] specifies the sub-picture index of the gridposition (i, j). The length of the syntax element is Ceil(Log2(max_subpics_minus1+1)) bits.The variables SubPicTop[subpic_grid_idx[i][j]],SubPicLeft[subpic_grid_idx[i][j]], SubPicWidth[subpic_grid_idx [i][j]],SubPicHeight[subpic_grid_idx[i][j]], and NumSubPics are derived asfollows:

NumSubPics = 0 for( i = 0; i. < NumSubPicGridRows; i++ ) {  for( j = 0;j < NumSubPicGridCols; j++ ) {   if (i = = 0)  SubPicTop[subpic_grid_idx[ i ][ j ] ] = 0   else if( subpic_grid_idx[ i ][ j] != subpic_grid_idx[ i − 1 ][ j ] ) {    SubPicTop[ subpic_grid_idx[ i][ j ] ] = i  SubPicHeight[ subpic_grid_idx[ i − 1][ j ] ] = i −SubPicTop[ subpic_grid_idx[ i − 1 ][ j ] ]   }   if (j = = 0)   SubPicLeft[ subpic_grid_idx[ i ][ j ] ] = 0   else if(subpic_grid_idx[ i ][ j ] != subpic_grid_idx[ i ][ j − 1 ] ) {   SubPicLeft[ subpic_grid_idx[ i ][ j ] ] = j  SubPicWidth[subpic_grid_idx[ i ][ j ] ] = j − SubPicLeft[ subpic_grid_idx[ i ][ j −1 ] ]   }   if ( i = = NumSubPicGridRows − 1)  SubPicHeight[subpic_grid_idx[ i ][ j ] ] = i − SubPicTop[ subpic_grid_idx[ i − 1 ][ j] ] + 1   if (j = = NumSubPicGridRows − 1)  SubPicWidth[subpic_grid_idx[ i ][ j ] ] = j − SubPicLeft[ subpic_grid_idx[ i ][ j −1 ] ] + 1   if( subpic_grid_idx[ i ][ j ] > NumSubPics)    NumSubPics =subpic_grid_idx[ i ][ j ]  } }subpic_treated_as_pic_flag[i] equal to 1 specifies that the i-thsub-picture of each coded picture in the CVS is treated as a picture inthe decoding process excluding in-loop filtering operations.subpic_treated_as_pic_flag[i] equal to 0 specifies that the i-thsub-picture of each coded picture in the CVS is not treated as a picturein the decoding process excluding in-loop filtering operations. When notpresent, the value of subpic_treated_as_pic_flag[i] is inferred to beequal to 0.loop_filter_across_subpic_enabled_flag[i] equal to 1 specifies thatin-loop filtering operations may be performed across the boundaries ofthe i-th sub-picture in each coded picture in the CVS.loop_filter_across_subpic_enabled_flag[i] equal to 0 specifies thatin-loop filtering operations are not performed across the boundaries ofthe i-th sub-picture in each coded picture in the CVS. When not present,the value of loop_filter_across_subpic_enabled_pic_flag[i] is inferredto be equal to 1.It is a requirement of bitstream conformance that the followingconstraints apply:

-   -   For any two sub-pictures subpicA and subpicB, when the index of        subpicA is less than the index of subpicB, any coded NAL unit of        subPicA shall succeed any coded NAL unit of subPicB in decoding        order.    -   The shapes of the sub-pictures shall be such that each        sub-picture, when decoded, shall have its entire left boundary        and entire top boundary consisting of picture boundaries or        consisting of boundaries of previously decoded sub-pictures.        The list CtbToSubPicIdx[ctbAddrRs] for ctbAddrRs ranging from 0        to PicSizeInCtbsY−1, inclusive, specifying the conversion from a        CTB address in picture raster scan to a sub-picture index, is        derived as follows:

for( ctbAddrRs = 0; ctbAddrRs < PicSizeInCtbsY; ctbAddrRs++ ) {  posX =ctbAddrRs % PicWidthInCtbsY * CtbSize Y  posY = ctbAddrRs /PicWidthInCtbs Y * CtbSize Y  CtbToSubPicIdx[ ctbAddrRs ] = − 1  for( i= 0; CtbToSubPicIdx[ ctbAddrRs ] < 0 && i < NumSubPics; i++ ) {   if( (posX >= SubPicLeft[ i ] * ( subpic_grid_col_width_minus1 + 1 ) * 4 ) &&    ( posX < ( SubPicLeft[ i ] + SubPicWidth[ i ] ) *       (subpic_grid_col_width_minus1 + 1 ) * 4 ) &&     ( posY >= SubPicTop[ i] *      ( subpic_grid_row_height_minus1 + 1 ) * 4 ) &&     ( posY < (SubPicTop[ i ] + SubPicHeight[ i ] ) *        (subpic_grid_row_height_minus1 + 1 ) * 4 ) )    CtbToSubPicIdx[ ctbAddrRs] = i  } }num_bricks_in_slice_minus1, when present, specifies the number of bricksin the slice minus 1. The value of num_bricks_in_slice_minus1 shall bein the range of 0 to NumBricksInPic−1, inclusive. When rect_slice_flagis equal to 0 and single_brick_per_slice_flag is equal to 1, the valueof num_bricks_in_slice_minus1 is inferred to be equal to 0. Whensingle_brick_per_slice_flag is equal to 1, the value ofnum_bricks_in_slice_minus1 is inferred to be equal to 0.The variable NumBricksInCurrSlice, which specifies the number of bricksin the current slice, and SliceBrickIdx[i], which specifies the brickindex of the i-th brick in the current slice, are derived as follows:

if( rect_slice_flag ) {  sliceIdx = 0  while( slice_address != slice_id[sliceIdx ] )   sliceIdx++  NumBricksInCurrSlice = NumBricksInSlice[sliceIdx ]  brickIdx = TopLeftBrickIdx[ sliceIdx ]  for( bIdx = 0;brickIdx <= BottomRightBrickIdx[ sliceIdx ]; brickIdx++ ) (7-92)   if(BricksToSliceMap[ brickIdx ] = = sliceIdx )    SliceBrickIdx[ bIdx++ ] =brickIdx } else {  NumBricksInCurrSlice = num_bricks_in_slice_minus1 + 1 SliceBrickIdx[ 0 ] = slice_address  for( i = 1; i <NumBricksInCurrSlice; i++ )   SliceBrickIdx[ i ] = SliceBrickIdx[ i − 1] + 1 }The variables SubPicIdx, SubPicLeftBoundaryPos, SubPicTopBoundaryPos,SubPicRightBoundaryPos, and SubPicBotBoundaryPos are derived as follows:

SubPicIdx = CtbToSubPicIdx[ CtbAddrBsToRs[ FirstCtbAddrBs[SliceBrickIdx[ 0 ] ] ] ] if( subpic_treated_as_pic_flag[ SubPicIdx ] ) {SubPicLeftBoundaryPos = SubPicLeft[ SubPicIdx ] * (subpic_grid_col_width_minus1 + 1 ) * 4 SubPicRightBoundaryPos = (SubPicLeft[ SubPicIdx ] + SubPicWidth[ SubPicIdx ] ) *  (subpic_grid_col_width_minus1 + 1 ) * 4 SubPicTopBoundaryPos = SubPicTop[SubPicIdx ] * ( subpic_grid_row_height_minus1 + 1 ) * 4SubPicBotBoundaryPos  =  ( SubPicTop[ SubPicIdx ] + SubPicHeight[SubPicIdx ] ) *  ( subpic_grid_row_height_minus1 + 1 ) * 4 } ...

Derivation Process for Temporal Luma Motion Vector Prediction

Inputs to this process are:

-   -   a luma location (xCb, yCb) of the top-left sample of the current        luma coding block relative to the top-left luma sample of the        current picture,    -   a variable cbWidth specifying the width of the current coding        block in luma samples,    -   a variable cbHeight specifying the height of the current coding        block in luma samples,    -   a reference index refIdxLX, with X being 0 or 1.        Outputs of this process are:    -   the motion vector prediction mvLXCol in 1/16 fractional-sample        accuracy,    -   the availability flag availableFlagLXCol.        The variable currCb specifies the current luma coding block at        luma location (xCb, yCb).        The variables mvLXCol and availableFlagLXCol are derived as        follows:    -   If slice_temporal_mvp_enabled_flag is equal to 0 or        (cbWidth*cbHeight) is less than or equal to 32, both components        of mvLXCol are set equal to 0 and availableFlagLXCol is set        equal to 0.    -   Otherwise (slice_temporal_mvp_enabled_flag is equal to 1), the        following ordered steps apply:    -   1. The bottom right collocated motion vector and the bottom and        right boundary sample locations are derived as follows:

xColBr=xCb+cbWidth  (8-421)

yColBr=yCb+cbHeight  (8-422)

rightBoundaryPos=subpic_treated_as_pic_flag[SubPicIdx]?SubPicRightBoundaryPos:pic_width_in_luma_samples−1  (8-423)

botBoundaryPos=subpic_treated_as_pic_flag[SubPicIdx]?SubPicBotBoundaryPos:pic_height_in_luma_samples−1  (8-424)

-   -   -   If yCb>>CtbLog2SizeY is equal to yColBr>>CtbLog2SizeY,            yColBr is less than or equal to botBoundaryPos and xColBr is            less than or equal to rightBoundaryPos, the following            applies:            -   The variable colCb specifies the luma coding block                covering the modified location given by ((xColBr>>3)<<3,                (yColBr>>3)<<3) inside the collocated picture specified                by ColPic.            -   The luma location (xColCb, yColCb) is set equal to the                top-left sample of the collocated luma coding block                specified by colCb relative to the top-left luma sample                of the collocated picture specified by ColPic.            -   The derivation process for collocated motion vectors as                specified in clause 8.5.2.12 is invoked with currCb,                colCb, (xColCb, yColCb), refIdxLX and sbFlag set equal                to 0 as inputs, and the output is assigned to mvLXCol                and availableFlagLXCol.                Otherwise, both components of mvLXCol are set equal to 0                and availableFlagLXCol is set equal to 0.                . . .

Luma Sample Bilinear Interpolation Process

Inputs to this process are:

-   -   a luma location in full-sample units (xInt_(L), yInt_(L)),    -   a luma location in fractional-sample units (xFrac_(L),        yFrac_(L)),    -   the luma reference sample array refPicLX_(L).        Output of this process is a predicted luma sample value        predSampleLX_(L)        The variables shift1, shift2, shift3, shift4, offset1, offset2        and offset3 are derived as follows:

shift1=BitDepth_(Y)−6  (8-453)

offset1=1<<(shift1−1)  (8-454)

shift2=4  (8-455)

offset2=1<<(shift2−1)  (8-456)

shift3=10−BitDepth_(Y)  (8-457)

shift4=BitDepth_(Y)−10  (8-458)

offset4=1<<(shift4−1)  (8-459)

The variable picW is set equal to pic_width_in_luma_samples and thevariable picH is set equal to pic_height_in_luma_samples.The luma interpolation filter coefficients fb_(L)[p] for each 1/16fractional sample position p equal to xFrac_(L) or yFrac_(L) arespecified in Table 8-10.The luma locations in full-sample units (xInt_(i), yInt_(i)) are derivedas follows for i=0 . . . 1:

-   -   If subpic_treated_as_pic_flag[SubPicIdx] is equal to 1, the        following applies:

xInt_(i)=Clip3(SubPicLeftBoundaryPos,SubPicRightBoundaryPos,xInt_(L)+i)  (8-460)

yInt_(i)=Clip3(SubPicTopBoundaryPos,SubPicBotBoundaryPos,yInt_(L)+i)  (8-461)

-   -   Otherwise (subpic_treated_as_pic_flag[SubPicIdx] is equal to 0),        the following applies:

xInt_(i)=Clip3(0,picW−1,sps_ref_wraparound_enabled_flag?ClipH((sps_ref_wraparound_offset_minus1+1)*MinCbSizeY,picW,(xInt_(L)+i)): xInt_(L) +i)  (8-462)

yInt_(i)=Clip3(0,picH−1,yInt_(L) +i)  (8-463)

. . .Derivation process for subblock-based temporal merging candidatesInputs to this process are:

-   -   a luma location (xCb, yCb) of the top-left sample of the current        luma coding block relative to the top-left luma sample of the        current picture,    -   a variable cbWidth specifying the width of the current coding        block in luma samples,    -   a variable cbHeight specifying the height of the current coding        block in luma samples.    -   the availability flag availableFlagA₁ of the neighbouring coding        unit,    -   the reference index refIdxLXA₁ of the neighbouring coding unit        with X being 0 or 1,    -   the prediction list utilization flag predFlagLXA₁ of the        neighbouring coding unit with X being 0 or 1,    -   the motion vector in 1/16 fractional-sample accuracy mvLXA₁ of        the neighbouring coding unit with X being 0 or 1.        Outputs of this process are:    -   the availability flag availableFlagSbCol,    -   the number of luma coding subblocks in horizontal direction        numSbX and in vertical direction numSbY,    -   the reference indices refIdxL0SbCol and refIdxL1SbCol,    -   the luma motion vectors in 1/16 fractional-sample accuracy        mvL0SbCol[xSbIdx][ySbIdx] and mvL1SbCol[xSbIdx][ySbIdx] with        xSbIdx=0 . . . numSbX−1, ySbIdx=0 . . . numSbY−1,    -   the prediction list utilization flags        predFlagL0SbCol[xSbIdx][ySbIdx] and        predFlagL1SbCol[xSbIdx][ySbIdx] with xSbIdx=0 . . . numSbX−1,        ySbIdx=0 . . . numSbY−1.        The availability flag availableFlagSbCol is derived as follows.    -   If one or more of the following conditions is true,        availableFlagSbCol is set equal to 0.        -   slice_temporal_mvp_enabled_flag is equal to 0.        -   sps_sbtmvp_enabled_flag is equal to 0.        -   cbWidth is less than 8.        -   cbHeight is less than 8.    -   Otherwise, the following ordered steps apply:        -   1. The location (xCtb, yCtb) of the top-left sample of the            luma coding tree block that contains the current coding            block and the location (xCtr, yCtr) of the below-right            center sample of the current luma coding block are derived            as follows:

xCtb=(xCb>>CtuLog2Size)<<CtuLog2Size  (8-542)

yCtb=(yCb>>CtuLog2Size)<<CtuLog2Size  (8-543)

xCtr=xCb+(cbWidth/2)  (8-544)

yCtr=yCb+(cbHeight/2)  (8-545)

-   -   -   2. The luma location (xColCtrCb, yColCtrCb) is set equal to            the top-left sample of the collocated luma coding block            covering the location given by (xCtr, yCtr) inside ColPic            relative to the top-left luma sample of the collocated            picture specified by ColPic.        -   3. The derivation process for subblock-based temporal            merging base motion data as specified in clause 8.5.5.4 is            invoked with the location (xCtb, yCtb), the location            (xColCtrCb, yColCtrCb), the availability flag            availableFlagA₁, and the prediction list utilization flag            predFlagLXA₁, and the reference index refIdxLXA₁, and the            motion vector mvLXA₁, with X being 0 and 1 as inputs and the            motion vectors ctrMvLX, and the prediction list utilization            flags ctrPredFlagLX of the collocated block, with X being 0            and 1, and the temporal motion vector tempMv as outputs.        -   4. The variable availableFlagSbCol is derived as follows:            -   If both ctrPredFlagL0 and ctrPredFlagL1 are equal to 0,                availableFlagSbCol is set equal to 0.            -   Otherwise, availableFlagSbCol is set equal to 1.                When availableFlagSbCol is equal to 1, the following                applies:

    -   The variables numSbX, numSbY, sbWidth, sbHeight and        refIdxLXSbCol are derived as follows:

numSbX=cbWidth>>3  (8-546)

numSbY=cbHeight>>3  (8-547)

sbWidth=cbWidth/numSbX  (8-548)

sbHeight=cbHeight/numSbY  (8-549)

refIdxLXSbCol=0  (8-550)

-   -   For xSbIdx=0 . . . numSbX−1 and ySbIdx=0 . . . numSbY−1, the        motion vectors mvLXSbCol[xSbIdx][ySbIdx] and prediction list        utilization flags predFlagLXSbCol[xSbIdx][ySbIdx] are derived as        follows:        -   The luma location (xSb, ySb) specifying the top-left sample            of the current coding subblock relative to the top-left luma            sample of the current picture is derived as follows:

xSb=xCb+xSbIdx*sbWidth+sbWidth/2  (8-551)

ySb=yCb+ySbIdx*sbHeight+sbHeight/2  (8-552)

-   -   -   The location (xColSb, yColSb) of the collocated subblock            inside ColPic is derived as follows.            -   The following applies:

yColSb=Clip3(yCtb,Min(CurPicHeightInSamplesY−1,yCtb+(1<<CtbLog2SizeY)−1),ySb+(tempMv[1]>>4))  (8-553)

-   -   -   -   If subpic_treated_as_pic_flag[SubPicIdx] is equal to 1,                the following applies:

xColSb=Clip3(xCtb,Min(SubPicRightBoundaryPos,xCtb+(1<<CtbLog2SizeY)+3),xSb+(tempMv[0]>>4))  (8-554)

-   -   -   -   Otherwise (subpic_treated_as_pic_flag[SubPicIdx] is                equal to 0), the following applies:

xColSb=Clip3(xCtb,Min(CurPicWidthInSamplesY−1,xCtb+(1<<CtbLog2SizeY)+3),xSb+(tempMv[0]>>4))  (8-555)

. . .

Derivation Process for Subblock-Based Temporal Merging Base Motion Data

Inputs to this process are:

-   -   the location (xCtb, yCtb) of the top-left sample of the luma        coding tree block that contains the current coding block,    -   the location (xColCtrCb, yColCtrCb) of the top-left sample of        the collocated luma coding block that covers the below-right        center sample.    -   the availability flag availableFlagA₁ of the neighbouring coding        unit,    -   the reference index refIdxLXA₁ of the neighbouring coding unit,    -   the prediction list utilization flag predFlagLXA₁ of the        neighbouring coding unit,    -   the motion vector in 1/16 fractional-sample accuracy mvLXA₁ of        the neighbouring coding unit.        Outputs of this process are:    -   the motion vectors ctrMvL0 and ctrMvL1,    -   the prediction list utilization flags ctrPredFlagL0 and        ctrPredFlagL1,    -   the temporal motion vector tempMv.        The variable tempMv is set as follows:

tempMv[0]=0  (8-558)

tempMv[1]=0  (8-559)

The variable currPic specifies the current picture.When availableFlagA₁ is equal to TRUE, the following applies:

-   -   If all of the following conditions are true, tempMv is set equal        to mvL0A₁:        -   predFlagL0A₁ is equal to 1,        -   DiffPicOrderCnt(ColPic, RefPicList[0][refIdxL0A₁]) is equal            to 0,    -   Otherwise, if all of the following conditions are true, tempMv        is set equal to mvL1A₁:        -   slice_type is equal to B,        -   predFlagL1A₁ is equal to 1,        -   DiffPicOrderCnt(ColPic, RefPicList[1][refIdxL1A₁]) is equal            to 0.            The location (xColCb, yColCb) of the collocated block inside            ColPic is derived as follows.    -   The following applies:

yColCb=Clip3(yCtb,Min(CurPicHeightInSamplesY−1,yCtb+(1<<CtbLog2SizeY)−1),yColCtrCb+(tempMv[1]>>4))  (8-560)

-   -   -   If subpic_treated_as_pic_flag[SubPicIdx] is equal to 1, the            following applies:

xColCb=Clip3(xCtb,Min(SubPicRightBoundaryPos,xCtb+(1<<CtbLog2SizeY)+3),xColCtrCb+(tempMv[0]>>4))  (8-561)

-   -   -   Otherwise (subpic_treated_as_pic_flag[SubPicIdx] is equal to            o, the following applies:

xColCb=Clip3(xCtb,Min(CurPicWidthInSamplesY−1,xCtb+(1<<CtbLog2SizeY)+3),xColCtrCb+(tempMv[0]>>4))  (8-562)

. . .Luma sample interpolation filtering process Inputs to this process are:

-   -   a luma location in full-sample units (xInt_(L), yInt_(L)),    -   a luma location in fractional-sample units (xFrac_(L),        yFrac_(L)),    -   a luma location in full-sample units (xSbInt_(L), ySbInt_(L))        specifying the top-left sample of the bounding block for        reference sample padding relative to the top-left luma sample of        the reference picture,    -   the luma reference sample array refPicLX_(L),    -   the half sample interpolation filter index hpelIfIdx,    -   a variable sbWidth specifying the width of the current subblock,    -   a variable sbHeight specifying the height of the current        subblock,    -   a luma location (xSb, ySb) specifying the top-left sample of the        current subblock relative to the top-left luma sample of the        current picture,        Output of this process is a predicted luma sample value        predSampleLX_(L)        The variables shift1, shift2 and shift3 are derived as follows:    -   The variable shift1 is set equal to Min(4, BitDepth_(Y)−8), the        variable shift2 is set equal to 6 and the variable shift3 is set        equal to Max(2, 14−BitDepth_(Y)).    -   The variable picW is set equal to pic_width_in_luma_samples and        the variable picH is set equal to pic_height_in_luma_samples.        The luma interpolation filter coefficients f_(L)[p] for each        1/16 fractional sample position p equal to xFrac_(L) or        yFrac_(L) are derived as follows:    -   If MotionModelIdc[xSb][ySb] is greater than 0, and sbWidth and        sbHeight are both equal to 4, the luma interpolation filter        coefficients f_(L)[p] are specified in Table 8-12.    -   Otherwise, the luma interpolation filter coefficients f_(L)[p]        are specified in Table 8-11 depending on hpelIfIdx.        The luma locations in full-sample units (xInt_(i), yInt_(i)) are        derived as follows for i=0 . . . 7:    -   If subpic_treated_as_pic_flag[SubPicIdx] is equal to 1, the        following applies:

xInt_(i)=Clip3(SubPicLeftBoundaryPos,SubPicRightBoundaryPos,xInt_(L)+i−3)  (8-771)

yInt_(i)=Clip3(SubPicTopBoundaryPos,SubPicBotBoundaryPos,yInt_(L)+i−3)  (8-772)

-   -   Otherwise (subpic_treated_as_pic_flag[SubPicIdx] is equal to 0),        the following applies:

xInt_(i)=Clip3(0,picW−1,sps_ref_wraparound_enabled_flag?ClipH((sps_ref_wraparound_offset_minus1+1)*MinCbSizeY,picW,xInt_(L)+i−3): xInt_(L) +i−3)  (8-773)

yInt_(i)=Clip3(0,picH−1,yInt_(L) +i−3)  (8-774)

. . .

Chroma Sample Interpolation Process

Inputs to this process are:

-   -   a chroma location in full-sample units (xInt_(C), yInt_(C)),    -   a chroma location in 1/32 fractional-sample units (xFrac_(C),        yFrac_(C)),    -   a chroma location in full-sample units (xSbIntC, ySbIntC)        specifying the top-left sample of the bounding block for        reference sample padding relative to the top-left chroma sample        of the reference picture,    -   a variable sbWidth specifying the width of the current subblock,    -   a variable sbHeight specifying the height of the current        subblock,    -   the chroma reference sample array refPicLX_(C).        Output of this process is a predicted chroma sample value        predSampleLX_(C)        The variables shift1, shift2 and shift3 are derived as follows:    -   The variable shift1 is set equal to Min(4, BitDepth_(C)−8), the        variable shift2 is set equal to 6 and the variable shift3 is set        equal to Max(2, 14−BitDepth_(C)).    -   The variable picW_(C) is set equal to        pic_width_in_luma_samples/SubWidthC and the variable picH_(C) is        set equal to pic_height_in_luma_samples/SubHeightC.        The chroma interpolation filter coefficients fc[p] for each 1/32        fractional sample position p equal to xFrac_(C) or yFrac_(C) are        specified in Table 8-13.        The variable xOffset is set equal to        (sps_ref_wraparound_offset_minus1+1)*MinCbSizeY)/SubWidthC.        The chroma locations in full-sample units (xInt_(i), yInt_(i))        are derived as follows for i=0 . . . 3:    -   If subpic_treated_as_pic_flag[SubPicIdx] is equal to 1, the        following applies:

xInt_(i)=Clip3(SubPicLeftBoundaryPos/SubWidthC,SubPicRightBoundaryPos/SubWidthC,xInt_(L)+i)   (8-785)

yInt_(i)=Clip3(SubPicTopBoundaryPos/SubHeightC,SubPicBotBoundaryPos/SubHeightC,yInt_(L)+i)  (8-786)

-   -   Otherwise (subpic_treated_as_pic_flag[SubPicIdx] is equal to 0),        the following applies:

xInt_(i)=Clip3(0,picW_(C)−1,sps_ref_wraparound_enabled_flag?ClipH(xOffset,picW_(C),xInt_(C) +i−1): xInt_(C) +i−1)  (8-787)

yInt_(i)=Clip3(0,picH _(C)−1,yInt_(C) +i−1)  (8-788)

2.4 Example Encoder-Only Group of Pictures (GOP)-Based Temporal Filter

In some embodiments, an encoder-only temporal filter can be implemented.The filtering is done at the encoder side as a pre-processing step.Source pictures before and after the selected picture to encode are readand a block based motion compensation method relative to the selectedpicture is applied on those source pictures. Samples in the selectedpicture are temporally filtered using sample values after motioncompensation.

The overall filter strength is set depending on the temporal sub layerof the selected picture as well as the QP. Only pictures at temporal sublayers 0 and 1 are filtered and pictures of layer 0 are filter by astronger filter than pictures of layer 1. The per sample filter strengthis adjusted depending on the difference between the sample value in theselected picture and the co-located samples in motion compensatedpictures so that small differences between a motion compensated pictureand the selected picture are filtered more strongly than largerdifferences.

GOP Based Temporal Filter

A temporal filter is introduced directly after reading picture andbefore encoding. Below are the steps described in more detail.

Operation 1: Pictures are read by the encoder

Operation 2: If a picture is low enough in the coding hierarchy, it isfiltered before encoding. Otherwise the picture is encoded withoutfiltering. Random Access (RA) pictures with picture order count (POC) %8==0 are filtered as well as Low Delay (LD) pictures with POC % 4==0.Artificial intelligence (AI) pictures are never filtered.

The overall filter strength, s_(o), is set according to the equationbelow for RA.

${s_{o}(n)} = \left\{ \begin{matrix}{1.5,} & {{n{mod}16} = 0} \\{0.95,} & {{n{mod}16} \neq 0}\end{matrix} \right.$

where n is the number of pictures read.

For the LD case, s_(o)(n)=0.95 is used.

Operation 3: Two pictures before and/or after the selected picture(referred to as original picture further down) are read. In the edgecases e.g. if is the first picture or close to the last picture, onlythe available pictures are read.

Operation 4: Motion of the read pictures before and after, relative tothe original picture is estimated per 8×8 picture block.

A hierarchical motion estimation scheme is used and the layers L0, L1and L2, are illustrated in FIG. 2 . Subsampled pictures are generated byaveraging each 2×2 block for all read pictures and the original picture,e.g. L1 in FIG. 1 . L2 is derived from L1 using the same subsamplingmethod.

FIG. 2 shows examples of different layers of the hierarchical motionestimation. L0 is the original resolution. L1 is a subsampled version ofL0. L2 is a subsampled version of L1.

First, motion estimation is done for each 16×16 block in L2. The squareddifference is calculated for each selected motion vector and the motionvector corresponding to the smallest difference is selected. Theselected motion vector is then used as initial value when estimating themotion in L1. Then the same is done for estimating motion in L0. As afinal step, subpixel motion is estimated for each 8×8 block by using aninterpolation filter on L0.

The VVC test model (VTM) 6-tap interpolation filter can used:

 0: 0,  0, 64,  0,  0, 0  1: 1, −3, 64,  4, −2, 0  2: 1, −6, 62,  9, −3,1  3: 2, −8, 60, 14, −5, 1  4: 2, −9, 57, 19, −7, 2  5: 3, −10,  53, 24,−8, 2  6: 3, −11,  50, 29, −9, 2  7: 3, −11,  44, 35, −10,  3  8: 1, −7,38, 38, −7, 1  9: 3, −10,  35, 44, −11,  3 10: 2, −9, 29, 50, −11,  311: 2, −8, 24, 53, −10,  3 12: 2, −7, 19, 57, −9, 2 13: 1, −5, 14, 60,−8, 2 14: 1, −3,  9, 62, −6, 1 15: 0, −2,  4, 64, −3, 1

Operation 5: Motion compensation is applied on the pictures before andafter the original picture according to the best matching motion foreach block, e.g., so that the sample coordinates of the original picturein each block have the best matching coordinates in the referencedpictures.

Operation 6: The samples of the processed one by one for the luma andchroma channels as described in the following steps.

Operation 7: The new sample value, I_(n), is calculated using thefollowing formula.

$I_{n} = \frac{I_{o} + {{\sum}_{i = 0}^{3}{w_{r}\left( {i,a} \right)}{I_{r}(i)}}}{1 + {{\sum}_{i = 0}^{3}{w_{r}\left( {i,a} \right)}}}$

Where I_(o) is the sample value of the original sample, I_(r)(i) is theintensity of the corresponding sample of motion compensated picture iand w_(r)(i, a) is the weight of motion compensated picture i when thenumber of available motion compensated pictures is a.

In the luma channel, the weights, w_(r)(i, a), is defined as follows:

${w_{r}\left( {i,a} \right)} = {s_{l}{s_{o}(n)}{s_{r}\left( {i,a} \right)}e^{- \frac{\Delta{I(i)}^{2}}{2{\sigma_{l}({QP})}^{2}}}}$

Where

s_(l) = 0.4 ${s_{r}\left( {i,2} \right)} = \left\{ \begin{matrix}{1.2,} & {i = 0} \\{1.,} & {i = 1}\end{matrix} \right.$${s_{r}\left( {i,4} \right)} = \left\{ \begin{matrix}{0.6,} & {i = 0} \\{0.85,} & {i = 1} \\{0.85,} & {i = 2} \\{0.6,} & {i = 3}\end{matrix} \right.$

For all other cases of i, and a: s_(r)(i, a)=0.3

σ_(l)(QP)=3*(QP−10)

ΔI(i)=I _(r)(i)−I _(o)

For the chroma channels, the weights, w_(r)(i, a), is defined asfollows:

${w_{r}\left( {i,a} \right)} = {s_{c}{s_{o}(n)}{s_{r}\left( {i,a} \right)}e^{- \frac{\Delta{I(i)}^{2}}{2\sigma_{c}^{2}}}}$

Where s_(c)=0.55 and σ_(c)=30

Operation 8: The filter is applied for the current sample. The resultingsample value is stored separately.

Operation 9: The filtered picture is encoded.

2.5 Example Picture Partitions (Tiles, Bricks, Slices)

In some embodiments, a picture is divided into one or more tile rows andone or more tile columns. A tile is a sequence of CTUs that covers arectangular region of a picture.

A tile is divided into one or more bricks, each of which consisting of anumber of CTU rows within the tile.

A tile that is not partitioned into multiple bricks is also referred toas a brick. However, a brick that is a true subset of a tile is notreferred to as a tile.

A slice either contains a number of tiles of a picture or a number ofbricks of a tile.

A sub-picture contains one or more slices that collectively cover arectangular region of a picture.

Two modes of slices are supported, namely the raster-scan slice mode andthe rectangular slice mode. In the raster-scan slice mode, a slicecontains a sequence of tiles in a tile raster scan of a picture. In therectangular slice mode, a slice contains a number of bricks of a picturethat collectively form a rectangular region of the picture. The brickswithin a rectangular slice are in the order of brick raster scan of theslice.

FIG. 5 shows an example of raster-scan slice partitioning of a picture,where the picture is divided into 12 tiles and 3 raster-scan slices.

FIG. 6 shows an example of rectangular slice partitioning of a picture,where the picture is divided into 24 tiles (6 tile columns and 4 tilerows) and 9 rectangular slices.

FIG. 7 shows an example of a picture partitioned into tiles, bricks, andrectangular slices, where the picture is divided into 4 tiles (2 tilecolumns and 2 tile rows), 11 bricks (the top-left tile contains 1 brick,the top-right tile contains 5 bricks, the bottom-left tile contains 2bricks, and the bottom-right tile contain 3 bricks), and 4 rectangularslices.

Picture Parameter Set RBSP Syntax

Descriptor pic_parameter_set_rbsp( ) { ...  single_tile_in_pic_flag u(1) if( !single_tile_in_pic_flag ) {   uniform_tile_spacing_flag u(1)   if(uniform_tile_spacing_flag ) {    tile_cols_width_minus1 ue(v)   tile_rows_height_minus1 ue(v)   } else {    num_tile_columns_minus1ue(v)    num_tile_rows_minus1 ue(v)    for( i = 0; i <num_tile_columns_minus1; i++ )     tile_column_width_minus1[ i ] ue(v)   for( i = 0; i < num_tile_rows_minus1; i++ )    tile_row_height_minus1[ i ] ue(v)   }   brick_splitting_present_flagu(1)   if( uniform_tile_spacing_flag && brick_splitting_present_flag )   num_tiles_in_pic_minus1 ue(v)   for( i = 0;brick_splitting_present_flag && i <= num_tiles_in_pic_minus1 + 1; i++ ){    if( RowHeight[ i ] > 1 )     brick_split_flag[ i ] u(1)    if(brick_split_flag[ i ] ) {     if( RowHeight[ i ] > 2 )     uniform_brick_spacing_flag[ i ] u(1)     if(uniform_brick_spacing_flag[ i ] )      brick_height_minus1[ i ] ue(v)    else {      num_brick_rows_minus2[ i ] ue(v)      for( j = 0; j <=num_brick_rows_minus2[ i ]; j++ )       brick_row_height_minus1[ i ][ j] ue(v)     }    }   }   single_brick_per_slice_flag u(1)   if(!single_brick_per_slice_flag )    rect_slice_flag u(1)   if(rect_slice_flag && !single_brick_per_slice_flag ) {   num_slices_in_pic_minus1 ue(v)   bottom_right_brick_idx_length_minus1 ue(v)    for( i = 0; i <num_slices_in_pic_minus1; i++ ) {     bottom_right_brick_idx_delta [ i ]u(v)     brick_idx_delta_sign_flag [ i ] u(1)    }   }  loop_filter_across_bricks_enabled_flag u(1)   if(loop_filter_across_bricks_enabled_flag )   loop_filter_across_slices_enabled_flag u(1)  }  if( rect_slice_flag ){   signalled_slice_id_flag u(1)   if( signalled_slice_id_flag ) {   signalled_slice_id_length_minus1 ue(v)    for( i = 0; i <=num_slices_in_pic_minus1; i++ )     slice_id[ i ] u(v)   }  } ...

Descriptor slice_header( ) {  slice_pic_parameter_set_id ue(v)  if(rect_slice_flag ∥ NumBricksInPic > 1 )   slice_address u(v)  if(!rect_slice_flag && !single_brick_per_slice_flag )  num_bricks_in_slice_minus1 ue(v)  non_reference_picture_flag u(1) slice_type ue(v) ...single_tile_in_pic_flag equal to 1 specifies that there is only one tilein each picture referring to the picture parameter set (PPS).single_tile_in_pic_flag equal to 0 specifies that there is more than onetile in each picture referring to the PPS.

-   -   NOTE—In absence of further brick splitting within a tile, the        whole tile is referred to as a brick. When a picture contains        only a single tile without further brick splitting, it is        referred to as a single brick.        It is a requirement of bitstream conformance that the value of        single_tile_in_pic_flag shall be the same for all PPSs that are        referred to by coded pictures within a CVS.        uniform_tile_spacing_flag equal to 1 specifies that tile column        boundaries and likewise tile row boundaries are distributed        uniformly across the picture and signalled using the syntax        elements tile_cols_width_minus1 and tile_rows_height_minus1.        uniform_tile_spacing_flag equal to 0 specifies that tile column        boundaries and likewise tile row boundaries may or may not be        distributed uniformly across the picture and signalled using the        syntax elements num_tile_columns_minus1 and num_tile_rows_minus1        and a list of syntax element pairs tile_column_width_minus1[i]        and tile_row_height_minus1[i]. When not present, the value of        uniform_tile_spacing_flag is inferred to be equal to 1.        tile_cols_width_minus1 plus 1 specifies the width of the tile        columns excluding the right-most tile column of the picture in        units of CTBs when uniform_tile_spacing_flag is equal to 1. The        value of tile_cols_width_minus1 shall be in the range of 0 to        PicWidthInCtbsY−1, inclusive. When not present, the value of        tile_cols_width_minus1 is inferred to be equal to        PicWidthInCtbsY−1.        tile_rows_height_minus1 plus 1 specifies the height of the tile        rows excluding the bottom tile row of the picture in units of        CTBs when uniform_tile_spacing_flag is equal to 1. The value of        tile_rows_height_minus1 shall be in the range of 0 to        PicHeightInCtbsY−1, inclusive. When not present, the value of        tile_rows_height_minus1 is inferred to be equal to        PicHeightInCtbsY−1.        num_tile_columns_minus1 plus 1 specifies the number of tile        columns partitioning the picture when uniform_tile_spacing_flag        is equal to 0. The value of num_tile_columns_minus1 shall be in        the range of 0 to PicWidthInCtbsY−1, inclusive. If        single_tile_in_pic_flag is equal to 1, the value of        num_tile_columns_minus1 is inferred to be equal to 0. Otherwise,        when uniform_tile_spacing_flag is equal to 1, the value of        num_tile_columns_minus1 is inferred as specified in clause        6.5.1.        num_tile_rows_minus1 plus 1 specifies the number of tile rows        partitioning the picture when uniform_tile_spacing_flag is equal        to 0. The value of num_tile_rows_minus1 shall be in the range of        0 to PicHeightInCtbsY−1, inclusive. If single_tile_in_pic_flag        is equal to 1, the value of num_tile_rows_minus1 is inferred to        be equal to 0. Otherwise, when uniform_tile_spacing_flag is        equal to 1, the value of num_tile_rows_minus1 is inferred as        specified in clause 6.5.1.        The variable NumTilesInPic is set equal to        (num_tile_columns_minus1+1)*(num_tile_rows_minus1+1).        When single_tile_in_pic_flag is equal to 0, NumTilesInPic shall        be greater than 1.        tile_column_width_minus1[i] plus 1 specifies the width of the        i-th tile column in units of CTBs.        tile_row_height_minus1[i] plus 1 specifies the height of the        i-th tile row in units of CTBs.        brick_splitting_present_flag equal to 1 specifies that one or        more tiles of pictures referring to the PPS may be divided into        two or more bricks. brick_splitting_present_flag equal to 0        specifies that no tiles of pictures referring to the PPS are        divided into two or more bricks.        num_tiles_in_pic_minus1 plus 1 specifies the number of tiles in        each picture referring to the PPS. The value of        num_tiles_in_pic_minus1 shall be equal to NumTilesInPic−1. When        not present, the value of num_tiles_in_pic_minus1 is inferred to        be equal to NumTilesInPic−1.        brick_split_flag[i] equal to 1 specifies that the i-th tile is        divided into two or more bricks. brick_split_flag[i] equal to 0        specifies that the i-th tile is not divided into two or more        bricks. When not present, the value of brick_split_flag[i] is        inferred to be equal to 0. In some embodiments, PPS parsing        dependency on SPS is introduced by adding the syntax condition        “if(RowHeight[i]>1)” (e.g., similarly for        uniform_brick_spacing_flag[i]).        uniform_brick_spacing_flag[i] equal to 1 specifies that        horizontal brick boundaries are distributed uniformly across the        i-th tile and signalled using the syntax element        brick_height_minus1[i]. uniform_brick_spacing_flag[i] equal to 0        specifies that horizontal brick boundaries may or may not be        distributed uniformly across i-th tile and signalled using the        syntax element num_brick_rows_minus2[i] and a list of syntax        elements brick_row_height_minus1[i][j]. When not present, the        value of uniform_brick_spacing_flag[i] is inferred to be equal        to 1.        brick_height_minus1[i] plus 1 specifies the height of the brick        rows excluding the bottom brick in the i-th tile in units of        CTBs when uniform_brick_spacing_flag[i] is equal to 1. When        present, the value of brick_height_minus1 shall be in the range        of 0 to RowHeight[i]−2, inclusive. When not present, the value        of brick_height_minus1[i] is inferred to be equal to        RowHeight[i]−1.        num_brick_rows_minus2[i] plus 2 specifies the number of bricks        partitioning the i-th tile when uniform_brick_spacing_flag[i] is        equal to 0. When present, the value of num_brick_rows_minus2[i]        shall be in the range of 0 to RowHeight[i]−2, inclusive. If        brick_split_flag[i] is equal to 0, the value of        num_brick_rows_minus2[i] is inferred to be equal to −1.        Otherwise, when uniform_brick_spacing_flag[i] is equal to 1, the        value of num_brick_rows_minus2[i] is inferred as specified in        6.5.1.        brick_row_height_minus1[i][j] plus 1 specifies the height of the        j-th brick in the i-th tile in units of CTBs when        uniform_tile_spacing_flag is equal to 0.        The following variables are derived, and, when        uniform_tile_spacing_flag is equal to 1, the values of        num_tile_columns_minus1 and num_tile_rows_minus1 are inferred,        and, for each i ranging from 0 to NumTilesInPic−1, inclusive,        when uniform_brick_spacing_flag[i] is equal to 1, the value of        num_brick_rows_minus2[i] is inferred, by invoking the CTB raster        and brick scanning conversion process as specified in clause        6.5.1:    -   the list RowHeight[j] for j ranging from 0 to        num_tile_rows_minus1, inclusive, specifying the height of the        j-th tile row in units of CTBs,    -   the list CtbAddrRsToBs[ctbAddrRs] for ctbAddrRs ranging from 0        to PicSizeInCtbsY−1, inclusive, specifying the conversion from a        CTB address in the CTB raster scan of a picture to a CTB address        in the brick scan,    -   the list CtbAddrBsToRs[ctbAddrBs] for ctbAddrBs ranging from 0        to PicSizeInCtbsY−1, inclusive, specifying the conversion from a        CTB address in the brick scan to a CTB address in the CTB raster        scan of a picture,    -   the list BrickId[ctbAddrBs] for ctbAddrBs ranging from 0 to        PicSizeInCtbsY−1, inclusive, specifying the conversion from a        CTB address in brick scan to a brick ID,    -   the list NumCtusInBrick[brickIdx] for brickIdx ranging from 0 to        NumBricksInPic−1, inclusive, specifying the conversion from a        brick index to the number of CTUs in the brick,    -   the list FirstCtbAddrBs[brickIdx] for brickIdx ranging from 0 to        NumBricksInPic−1, inclusive, specifying the conversion from a        brick ID to the CTB address in brick scan of the first CTB in        the brick.        single_brick_per_slice_flag equal to 1 specifies that each slice        that refers to this PPS includes one brick.        single_brick_per_slice_flag equal to 0 specifies that a slice        that refers to this PPS may include more than one brick. When        not present, the value of single_brick_per_slice_flag is        inferred to be equal to 1.        rect_slice_flag equal to 0 specifies that bricks within each        slice are in raster scan order and the slice information is not        signalled in PPS. rect_slice_flag equal to 1 specifies that        bricks within each slice cover a rectangular region of the        picture and the slice information is signalled in the PPS. When        brick_splitting_present_flag is equal to 1, the value of        rect_slice_flag shall be equal to 1. When not present,        rect_slice_flag is inferred to be equal to 1.        num_slices_in_pic_minus1 plus 1 specifies the number of slices        in each picture referring to the PPS. The value of        num_slices_in_pic_minus1 shall be in the range of 0 to        NumBricksInPic−1, inclusive. When not present and        single_brick_per_slice_flag is equal to 1, the value of        num_slices_in_pic_minus1 is inferred to be equal to        NumBricksInPic−1.        bottom_right_brick_idx_length_minus1 plus 1 specifies the number        of bits used to represent the syntax element        bottom_right_brick_idx_delta[i]. The value of        bottom_right_brick_idx_length_minus1 shall be in the range of 0        to Ceil(Log 2(NumBricksInPic))−1, inclusive.        bottom_right_brick_idx_delta[i] when i is greater than 0        specifies the difference between the brick index of the brick        located at the bottom-right corner of the i-th slice and and the        brick index of the bottom-right corner of the (i−1)-th slice.        bottom_right_brick_idx_delta[0] specifies the brick index of the        bottom right corner of the 0-th slice. When        single_brick_per_slice_flag is equal to 1, the value of        bottom_right_brick_idx_delta[i] is inferred to be equal to 1.        The value of the BottomRightBrickIdx[num_slices_in_pic_minus1]        is inferred to be equal to NumBricksInPic−1. The length of the        bottom_right_brick_idx_delta[i] syntax element is        bottom_right_brick_idx_length_minus1+1 bits.        brick_idx_delta_sign_flag[i] equal to 1 indicates a positive        sign for bottom_right_brick_idx_delta[i].        sign_bottom_right_brick_idx_delta[i] equal to 0 indicates a        negative sign for bottom_right_brick_idx_delta[i].        It is a requirement of bitstream conformance that a slice shall        include either a number of complete tiles or only a consecutive        sequence of complete bricks of one tile.        The variable TopLeftBrickIdx[i], BottomRightBrickIdx[i],        NumBricksInSlice[i] and BricksToSliceMap[j], which specify the        brick index of the brick located at the top left corner of the        i-th slice, the brick index of the brick located at the bottom        right corner of the i-th slice, the number of bricks in the i-th        slice and the mapping of bricks to slices, are derived as        follows:

for( j = 0; i = = 0 && j < NumBricksInPic; j++ )  BricksToSliceMap[ j ]= −1 NumBricksInSlice[ i ] = 0 BottomRightBrickIdx[ i ] =bottom_right_brick_idx_delta[ i ] ] +( ( i = = 0 ) ? 0 :    (brick_idx_delta_sign_flag[ i ] ? BottomRightBrickIdx[ i − 1 ] :−BottomRightBrickIdx[ i−1 ] ) for( j = BottomRightBrickIdx[ i ]; j >= 0;j− − ) {  if( BrickColBd[ j ] <= BrickColBd[ BottomRightBrickIdx[ i ] ]&& (7-43)    BrickRowBd[ j ] <= BrickRowBd[ BottomRightBrickIdx[ i ] ]&&   BricksToSliceMap[ j ] = = −1 ) {   TopLeftBrickIdx[ i ] = j  NumBricksInSlice[ i ]++   BricksToSliceMap[ j ] = i  } }

General Slice Header Semantics

When present, the value of each of the slice header syntax elementsslice_pic_parameter_set_id, non_reference_picture_flag, colour_plane_id,slice_pic_order_cnt_lsb, recovery_poc_cnt, no_output_of_prior_pics_flag,pic_output_flag, and slice_temporal_mvp_enabled_flag shall be the samein all slice headers of a coded picture.The variable CuQpDeltaVal, specifying the difference between a lumaquantization parameter for the coding unit containing cu_qp_delta_absand its prediction, is set equal to 0. The variables CuQpOffset_(Cb),CuQpOffset_(Cr), and CuQpOffset_(CbCr), specifying values to be usedwhen determining the respective values of the Qp′_(Cb), Qp′_(Cr), andQp′_(CbCr) quantization parameters for the coding unit containingcu_chroma_qp_offset_flag, are all set equal to 0.slice_pic_parameter_set_id specifies the value ofpps_pic_parameter_set_id for the PPS in use. The value ofslice_pic_parameter_set_id shall be in the range of 0 to 63, inclusive.It is a requirement of bitstream conformance that the value ofTemporalId of the current picture shall be greater than or equal to thevalue of TemporalId of the PPS that has pps_pic_parameter_set_id equalto slice_pic_parameter_set_id.slice_address specifies the slice address of the slice. When notpresent, the value of slice_address is inferred to be equal to 0.If rect_slice_flag is equal to 0, the following applies:

-   -   The slice address is the brick ID as specified by Equation        (7-59).    -   The length of slice_address is Ceil(Log 2 (NumBricksInPic))        bits.    -   The value of slice_address shall be in the range of 0 to        NumBricksInPic−1, inclusive.        Otherwise (rect_slice_flag is equal to 1), the following        applies:    -   The slice address is the slice ID of the slice.    -   The length of slice_address is        signalled_slice_id_length_minus1+1 bits.    -   If signalled_slice_id_flag is equal to 0, the value of        slice_address shall be in the range of 0 to        num_slices_in_pic_minus1, inclusive. Otherwise, the value of        slice_address shall be in the range of 0 to        2^((signalled_slice_id_length_minus1+1))−1, inclusive.        It is a requirement of bitstream conformance that the following        constraints apply:    -   The value of slice_address shall not be equal to the value of        slice_address of any other coded slice NAL unit of the same        coded picture.    -   When rect_slice_flag is equal to 0, the slices of a picture        shall be in increasing order of their slice_address values.    -   The shapes of the slices of a picture shall be such that each        brick, when decoded, shall have its entire left boundary and        entire top boundary consisting of a picture boundary or        consisting of boundaries of previously decoded brick(s).        num_bricks_in_slice_minus1, when present, specifies the number        of bricks in the slice minus 1. The value of        num_bricks_in_slice_minus1 shall be in the range of 0 to        NumBricksInPic−1, inclusive. When rect_slice_flag is equal to 0        and single_brick_per_slice_flag is equal to 1, the value of        num_bricks_in_slice_minus1 is inferred to be equal to 0. When        single_brick_per_slice_flag is equal to 1, the value of        num_bricks_in_slice_minus1 is inferred to be equal to 0.        The variable NumBricksInCurrSlice, which specifies the number of        bricks in the current slice, and SliceBrickIdx[i], which        specifies the brick index of the i-th brick in the current        slice, are derived as follows:

if( rect_slice_flag ) {  sliceIdx = 0  while( slice_address != slice_id[sliceIdx ] )   sliceIdx++  NumBricksInCurrSlice = NumBricksInSlice[sliceIdx ]  brickIdx = TopLeftBrickIdx[ sliceIdx ]  for( bIdx = 0;brickIdx <= BottomRightBrickIdx[ sliceIdx ]; brickIdx++ ) (7-92)   if(BricksToSliceMap[ brickIdx ] = = sliceIdx )    SliceBrickIdx[ bIdx++ ] =brickIdx } else {  NumBricksInCurrSlice = num_bricks_in_slice_minus1 + 1 SliceBrickIdx[ 0 ] = slice_address  for( i = 1; i <NumBricksInCurrSlice; i++ )   SliceBrickIdx[ i ] = SliceBrickIdx[ i − 1] + 1 }The variables SubPicIdx, SubPicLeftBoundaryPos, SubPicTopBoundaryPos,SubPicRightBoundaryPos, and SubPicBotBoundaryPos are derived as follows:

SubPicIdx = CtbToSubPicIdx[ CtbAddrBsToRs[ FirstCtbAddrBs[SliceBrickIdx[ 0 ] ] ] ] if( subpic_treated_as_pic_flag[ SubPicIdx ] ) { SubPicLeftBoundaryPos = SubPicLeft[ SubPicIdx ] * (subpic_grid_col_width_minus1 + 1 ) * 4  SubPicRightBoundaryPos = (SubPicLeft[ SubPicIdx ] + SubPicWidth[ SubPicIdx ] ) *   (subpic_grid_col_width_minus1 + 1 ) * 4 (7-93)  SubPicTopBoundaryPos =SubPicTop[ SubPicIdx ] * ( subpic_grid_row_height_minus1 + 1 )* 4 SubPicBotBoundaryPos = ( SubPicTop[ SubPicIdx ] + SubPicHeight[SubPicIdx ] ) *   ( subpic_grid_row_height_minus1 + 1 ) * 4 }

2.6 Example Syntax and Semantics Sequence Parameter Set RBSP Syntax

Descriptor seq_parameter_set_rbsp( ) {  sps_decoding_parameter_set_idu(4)  sps_video_parameter_set_id u(4)  sps_max_sub_layers_minus1 u(3) sps_reserved_zero_5bits u(5)  profile_tier_level(sps_max_sub_layers_minus1 )  gdr_enabled_flag u(1) sps_seq_parameter_set_id u(4)  chroma_format_idc u(2)  if(chroma_format_idc = = 3 )   separate_colour_plane_flag u(1) ref_pic_resampling_enabled_flag u(1)  sps_seq_parameter_set_id ue(v) chroma_format_idc ue(v)  if( chroma_format_idc = = 3 )  separate_colour_plane_flag u(1)  pic_width_max_in_luma_samples ue(v) pic_height_max_in_luma_samples ue(v)  sps_log2_ctu_size_minus5 u(2)  

  

  

 

   

   

   

   

   

   

 

  

 

 

 

 

  

 

  

 

   

   

 

    

  

 

 bit_depth_minus8 ue(v)  min_qp_prime_ts_minus4 ue(v) sps_weighted_pred_flag u(1)  sps_weighted_bipred_flag u(1) log2_max_pic_order_cnt_lsb_minus4 u(4)  if( sps_max_sub_layers_minus1 >0 )   sps_sub_layer_ordering_info_present_flag u(1)  for( i = (sps_sub_layer_ordering_info_present_flag ? 0 : sps_max_sub_layers_minus1);    i <= sps_max_sub_layers_minus1; i++ ) {  sps_max_dec_pic_buffering_minus1[ i ] ue(v)  sps_max_num_reorder_pics[ i ] ue(v)   sps_max_latency_increase_plus1[i ] ue(v)  }  long_term_ref_pics_flag u(1) inter_layer_ref_pics_present_flag u(1)  sps_idr_rpl_present_flag u(1) rpl1_same_as_rpl0_flag u(1)  for( i = 0; i < !rpl1_same_as_rpl0_flag ?2 : 1; i++ ) {   num_ref_pic_lists_in_sps[ i ] ue(v)   for( j = 0; j <num_ref_pic_lists_in_sps[ i ]; j++)    ref_pic_list_struct( i, j )  } if( ChromaArrayType != 0 )   qtbtt_dual_tree_intra_flag u(1) log2_min_luma_coding_block_size_minus2 ue(v) partition_constraints_override_enabled_flag u(1) sps_log2_diff_min_qt_min_cb_intra_slice_luma ue(v) sps_log2_diff_min_qt_min_cb_inter_slice ue(v) sps_max_mtt_hierarchy_depth_inter_slice ue(v) sps_max_mtt_hierarchy_depth_intra_slice_luma ue(v)  if(sps_max_mtt_hierarchy_depth_intra_slice_luma != 0 ) {  sps_log2_diff_max_bt_min_qt_intra_slice_luma ue(v)  sps_log2_diff_max_tt_min_qt_intra_slice_luma ue(v)  }  if(sps_max_mtt_hierarchy_depth_inter_slice != 0 ) {  sps_log2_diff_max_bt_min_qt_inter_slice ue(v)  sps_log2_diff_max_tt_min_qt_inter_slice ue(v)  }  if(qtbtt_dual_tree_intra_flag ) {  sps_log2_diff_min_qt_min_cb_intra_slice_chroma ue(v)  sps_max_mtt_hierarchy_depth_intra_slice_chroma ue(v)   if(sps_max_mtt_hierarchy_depth_intra_slice_chroma != 0 ) {   sps_log2_diff_max_bt_min_qt_intra_slice_chroma ue(v)   sps_log2_diff_max_tt_min_qt_intra_slice_chroma ue(v)   }  } sps_max_luma_transform_size_64_flag u(1)  sps_joint_cbcr_enabled_flagu(1)  if( ChromaArrayType != 0 ) {   same_qp_table_for_chroma u(1)  numQpTables = same_qp_table_for_chroma ? 1 : (sps_joint_cbcr_enabled_flag ? 3 : 2 )   for( i = 0; i < numQpTables; i++) {    qp_table_start_minus26[ i ] se(v)   num_points_in_qp_table_minus1[ i ] ue(v)    for( j = 0; j <=num_points_in_qp_table_minus1[ i ]; j++ ) {     delta_qp_in_val_minus1[i ][ j ] ue(v)     delta_qp_diff_val[ i ][ j ] ue(v)    }   }  } sps_sao_enabled_flag u(1)  sps_alf_enabled_flag u(1) sps_transform_skip_enabled_flag u(1)  if(sps_transform_skip_enabled_flag )   sps_bdpcm_enabled_flag u(1)  if(sps_bdpcm_enabled_flag && chroma_format_idc = = 3 )  sps_bdpcm_chroma_enabled_flag u(1)  sps_ref_wraparound_enabled_flagu(1)  if( sps_ref_wraparound_enabled_flag )  sps_ref_wraparound_offset_minus1 ue(v)  sps_temporal_mvp_enabled_flagu(1)  if( sps_temporal_mvp_enabled_flag )   sps_sbtmvp_enabled_flag u(1) sps_amvr_enabled_flag u(1)  sps_bdof_enabled_flag u(1)  if(sps_bdof_enabled_flag )   sps_bdof_pic_present_flag u(1) sps_smvd_enabled_flag u(1)  sps_dmvr_enabled_flag u(1)  if(sps_dmvr_enabled_flag )   sps_dmvr_pic_present_flag u(1) sps_mmvd_enabled_flag u(1)  sps_isp_enabled_flag u(1) sps_mrl_enabled_flag u(1)  sps_mip_enabled_flag u(1)  if(ChromaArrayType != 0 )   sps_cclm_enabled_flag u(1)   if(sps_cclm_enabled_flag && chroma_format_idc = = 1 )  sps_cclm_colocated_chroma_flag u(1)  sps_mts_enabled_flag u(1)  if(sps_mts_enabled_flag ) {   sps_explicit_mts_intra_enabled_flag u(1)  sps_explicit_mts_inter_enabled_flag u(1)  }  sps_sbt_enabled_flag u(1) sps_affine_enabled_flag u(1)  if( sps_affine_enabled_flag ) {  sps_affine_type_flag u(1)   sps_affine_amvr_enabled_flag u(1)  sps_affine_prof_enabled_flag u(1)   if( sps_affine_prof_enabled_flag )   sps_prof_pic_present_flag u(1)  }  if( chroma_format_idc = = 3 ) {  sps_palette_enabled_flag u(1)   sps_act_enabled_flag u(1)  } sps_bcw_enabled_flag u(1)  sps_ibc_enabled_flag u(1) sps_ciip_enabled_flag u(1)  if( sps_mmvd_enabled_flag )  sps_fpel_mmvd_enabled_flag u(1)  sps_triangle_enabled_flag u(1) sps_lmcs_enabled_flag u(1)  sps_lfnst_enabled_flag u(1) sps_ladf_enabled_flag u(1)  if( sps_ladf_enabled_flag ) {  sps_num_ladf_intervals_minus2 u(2)  sps_ladf_lowest_interval_qp_offset se(v)   for( i = 0; i <sps_num_ladf_intervals_minus2 + 1; i++ ) {    sps_ladf_qp_offset[ i ]se(v)    sps_ladf_delta_threshold_minus1[ i ] ue(v)   }  } sps_scaling_list_enabled_flag u(1) sps_loop_filter_across_virtual_boundaries_disabled_present_flag u(1) if( sps_loop_filter_across_virtual_boundaries_disabled_present_flag ) {  sps_num_ver_virtual_boundaries u(2)   for( i = 0; i <sps_num_ver_virtual_boundaries; i++ )    sps_virtual_boundaries_pos_x[ i] u(13)   sps_num_hor_virtual_boundaries u(2)   for( i = 0; i <sps_num_hor_virtual_boundaries; i++ )    sps_virtual_boundaries_pos_y[ i] u(13)  }  general_hrd_parameters_present_flag u(1)  if(general_hrd_parameters_present_flag ) {   num_units_in_tick u(32)  time_scale u(32)   sub_layer_cpb_parameters_present_flag u(1)   if(sub_layer_cpb_parameters_present_flag )    general_hrd_parameters( 0,sps_max_sub_layers_minus1 )   else    general_hrd_parameters(sps_max_sub_layers_minus1, sps_max_sub_layers_minus1 )  } vui_parameters_present_flag u(1)  if( vui_parameters_present_flag )  vui_parameters( )  sps_extension_flag u(1)  if( sps_extension_flag )  while( more_rbsp_data( ) )    sps_extension_data_flag u(1) rbsp_trailing_bits( ) }

Picture Parameter Set RBSP Syntax

Descriptor pic_parameter_set_rbsp( ) {  pps_pic_parameter_set_id ue(v) pps_seq_parameter_set_id u(4)  pps_seq_parameter_set_id ue(v) pic_width_in_luma_samples ue(v)  pic_height_in_luma_samples ue(v) conformance_window_flag u(1)  if( conformance_window_flag ) {  conf_win_left_offset ue(v)   conf_win_right_offset ue(v)  conf_win_top_offset ue(v)   conf_win_bottom_offset ue(v)  } scaling_window_flag u(1)  if( scaling_window_flag ) {  scaling_win_left_offset ue(v)   scaling_win_right_offset ue(v)  scaling_win_top_offset ue(v)   scaling_win_bottom_offset ue(v)  } output_flag_present_flag u(1)  mixed_nalu_types_in_pic_flag u(1)  

 

 

 

  

  

  

 

   

 

 no_pic_partition_flag u(1)  if( !no_pic_partition_flag ) {  pps_log2_ctu_size_minus5 u(2)   num_exp_tile_columns_minus1 ue(v)  num_exp_tile_rows_minus1 ue(v)   for( i = 0; i <=num_exp_tile_columns_minus1; i++ )    tile_column_width_minus1[ i ]ue(v)   for( i = 0; i <= num_exp_tile_rows_minus1; i++ )   tile_row_height_minus1[ i ] ue(v)   rect_slice_flag u(1)   if(rect_slice_flag )    single_slice_per_subpic_flag u(1)   if(rect_slice_flag && !single_slice_per_subpic_flag ) {   num_slices_in_pic_minus1 ue(v)    tile_idx_delta_present_flag u(1)   for( i = 0; i < num_slices_in_pic_minus1; i++ ) {    slice_width_in_tiles_minus1[ i ] ue(v)    slice_height_in_tiles_minus1[ i ] ue(v)     if(slice_width_in_tiles_minus1[ i ] = = 0 &&       slice_height_in_tiles_minus1[ i ] = = 0 ) {     num_slices_in_tile_minus1[ i ] ue(v)      numSlicesInTileMinus1 =num_slices_in_tile_minus1[ i ]      for( j = 0; j <numSlicesInTileMinus1; j++ )       slice_height_in_ctu_minus1[ i++ ]ue(v)     }     if( tile_idx_delta_present_flag && i <num_slices_in_pic_minus1 )      tile_idx_delta[ i ] se(v)    }   }  loop_filter_across_tiles_enabled_flag u(1)  loop_filter_across_slices_enabled_flag u(1)  } entropy_coding_sync_enabled_flag u(1)  if( !no_pic_partition_flag ∥entropy_coding_sync_enabled_flag )   entry_point_offsets_present_flagu(1)  cabac_init_present_flag u(1)  for( i = 0; i < 2; i++ )  num_ref_idx_default_active_minus1[ i ] ue(v)  rpl1_idx_present_flagu(1)  init_qp_minus26 se(v)  

 

  

 

 cu_qp_delta_enabled_flag u(1)  pps_cb_qp_offset se(v)  pps_cr_qp_offsetse(v)  pps_joint_cbcr_qp_offset_present_flag u(1)  if(pps_joint_cbcr_qp_offset_present_flag )   pps_joint_cbcr_qp_offset_valuese(v)  pps_slice_chroma_qp_offsets_present_flag u(1) cu_chroma_qp_offset_enabled_flag u(1)  if(cu_chroma_qp_offset_enabled_flag ) {   chroma_qp_offset_list_len_minus1ue(v)   for( i = 0; i <= chroma_qp_offset_list_len_minus1; i++ ) {   cb_qp_offset_list[ i ] se(v)    cr_qp_offset_list[ i ] se(v)    if(pps_joint_cbcr_qp_offset_present_flag )     joint_cbcr_qp_offset_list[ i] se(v)   }  }  pps_weighted_pred_flag u(1)  pps_weighted_bipred_flagu(1)  deblocking_filter_control_present_flag u(1)  if(deblocking_filter_control_present_flag ) {  deblocking_filter_override_enabled_flag u(1)  pps_deblocking_filter_disabled_flag u(1)   if(!pps_deblocking_filter_disabled_flag ) {    pps_beta_offset_div2 se(v)   pps_tc_offset_div2 se(v)   }  } constant_slice_header_params_enabled_flag u(1)  if(constant_slice_header_params_enabled_flag ) {  pps_dep_quant_enabled_idc u(2)   for( i = 0; i < 2; i++ )   pps_ref_pic_list_sps_idc[ i ] u(2)   pps_mvd_l1_zero_idc u(2)  pps_collocated_from_l0_idc u(2)  pps_six_minus_max_num_merge_cand_plus1 ue(v)  pps_max_num_merge_cand_minus_max_num_triangle_cand_plus1 ue(v)  } picture_header_extension_present_flag u(1) slice_header_extension_present_flag u(1)  pps_extension_flag u(1)  if(pps_extension_flag )   while( more_rbsp_data( ) )   pps_extension_data_flag u(1)  rbsp_trailing_bits( ) }

Picture Header RBSP Syntax

Descriptor picture_header_rbsp( ) {  non_reference_picture_flag u(1) gdr_pic_flag u(1)  no_output_of_prior_pics_flag u(1)  if( gdr_pic_flag)   recovery_poc_cnt ue(v)  ph_pic_parameter_set_id ue(v)  

 

 

  

 

  

 

   

   

 

    

  

 

 if( !sps_loop_filter_across_virtual_boundaries_disabled_present_flag ){   ph_loop_filter_across_virtual_boundaries_disabled_present_flag u(1)  if( ph_loop_filter_across_virtual_boundaries_disabled_present_flag ) {   ph_num_ver_virtual_boundaries u(2)    for( i = 0; i <ph_num_ver_virtual_boundaries; i++ )     ph_virtual_boundaries_pos_x[ i] u(13)    ph_num_hor_virtual_boundaries u(2)    for( i = 0; i <ph_num_hor_virtual_boundaries; i++ )     ph_virtual_boundaries_pos_y[ i] u(13)   }  }  if( separate_colour_plane_flag = = 1 )   colour_plane_idu(2)  if( output_flag_present_flag )   pic_output_flag u(1) pic_rpl_present_flag u(1)  if( pic_rpl_present_flag ) {   for( i = 0; i< 2; i++ ) {    if( num_ref_pic_lists_in_sps[ i ] > 0 &&!pps_ref_pic_list_sps_idc[ i ] &&       (i = = 0 ∥ (i = = 1 &&rpl1_idx_present_flag) ) )     pic_rpl_sps_flag[ i ] u(1)    if(pic_rpl_sps_flag[ i ] ) {     if( num_ref_pic_lists_in_sps[ i ] > 1 &&       (i = = 0 ∥ ( i = = 1 && rpl1_idx_present_flag) ) )     pic_rpl_idx[ i ] u(v)    } else     ref_pic_list_struct( i,num_ref_pic_lists_in_sps[ i ] )    for( j = 0; j < NumLtrpEntries[ i ][RplsIdx[ i ] ]; j++ ) {     if( ltrp_in_slice_header_flag[ i ][ RplsIdx[i ] ] )      pic_poc_lsb_lt[ i ][ j ] u(v)    pic_delta_poc_msb_present_flag[ i ][ j ] u(1)     if(pic_delta_poc_msb_present_flag[ i ][ j ] )     pic_delta_poc_msb_cycle_lt[ i ][ j ] ue(v)    }   }  }  if(partition_constraints_override_enabled_flag ) {  partition_constraints_override_flag ue(v)   if(partition_constraints_override_flag ) {   pic_log2_diff_min_qt_min_cb_intra_slice_luma ue(v)   pic_log2_diff_min_qt_min_cb_inter_slice ue(v)   pic_max_mtt_hierarchy_depth_inter_slice ue(v)   pic_max_mtt_hierarchy_depth_intra_slice_luma ue(v)    if(pic_max_mtt_hierarchy_depth_intra_slice_luma != 0 ) {    pic_log2_diff_max_bt_min_qt_intra_slice_luma ue(v)    pic_log2_diff_max_tt_min_qt_intra_slice_luma ue(v)    }    if(pic_max_mtt_hierarchy_depth_inter_slice != 0 ) {    pic_log2_diff_max_bt_min_qt_inter_slice ue(v)    pic_log2_diff_max_tt_min_qt_inter_slice ue(v)    }    if(qtbtt_dual_tree_intra_flag ) {    pic_log2_diff_min_qt_min_cb_intra_slice_chroma ue(v)    pic_max_mtt_hierarchy_depth_intra_slice_chroma ue(v)     if(pic_max_mtt_hierarchy_depth_intra_slice_chroma != 0 ) {     pic_log2_diff_max_bt_min_qt_intra_slice_chroma ue(v)     pic_log2_diff_max_tt_min_qt_intra_slice_chroma ue(v)     }    }   } }  if( cu_qp_delta_enabled_flag ) {  pic_cu_qp_delta_subdiv_intra_slice ue(v)  pic_cu_qp_delta_subdiv_inter_slice ue(v)  }  if(cu_chroma_qp_offset_enabled_flag ) {  pic_cu_chroma_qp_offset_subdiv_intra_slice ue(v)  pic_cu_chroma_qp_offset_subdiv_inter_slice ue(v)  }  if(sps_temporal_mvp_enabled_flag )   pic_temporal_mvp_enabled_flag u(1) if(!pps_mvd_l1_zero_idc )   mvd_l1_zero_flag u(1)  if(!pps_six_minus_max_num_merge_cand_plus1 )  pic_six_minus_max_num_merge_cand ue(v)  if( sps_affine_enabled_flag )  pic_five_minus_max_num_subblock_merge_cand ue(v)  if(sps_fpel_mmvd_enabled_flag )   pic_fpel_mmvd_enabled_flag u(1)  if(sps_bdof_pic_present_flag )   pic_disable_bdof_flag u(1)  if(sps_dmvr_pic_present_flag )   pic_disable_dmvr_flag u(1)  if(sps_prof_pic_present_flag )   pic_disable_prof_flag u(1)  if(sps_triangle_enabled_flag && MaxNumMergeCand >= 2 &&   !pps_max_num_merge_cand_minus_max_num_triangle_cand_minus1 )  pic_max_num_merge_cand_minus_max_num_triangle_cand ue(v)  if (sps_ibc_enabled_flag )   pic_six_minus_max_num_ibc_merge_cand ue(v)  if(sps_joint_cbcr_enabled_flag )   pic_joint_cbcr_sign_flag u(1)  if(sps_sao_enabled_flag ) {   pic_sao_enabled_present_flag u(1)   if(pic_sao_enabled_present_flag ) {    pic_sao_luma_enabled_flag u(1)   if(ChromaArrayType != 0 )     pic_sao_chroma_enabled_flag u(1)   }  } if( sps_alf_enabled_flag ) {   pic_alf_enabled_present_flag u(1)   if(pic_alf_enabled_present_flag ) {    pic_alf_enabled_flag u(1)    if(pic_alf_enabled_flag ) {     pic_num_alf_aps_ids_luma u(3)     for( i =0; i < pic_num_alf_aps_ids_luma; i++ )      pic_alf_aps_id_luma[ i] u(3)    if( ChromaArrayType != 0 )      pic_alf_chroma_idc u(2)     if(pic_alf_chroma_idc )      pic_alf_aps_id_chroma u(3)    }   }  }  if (!pps_dep_quant_enabled_flag )   pic_dep_quant_enabled_flag u(1)  if(!pic_dep_quant_enabled_flag )   sign_data_hiding_enabled_flag u(1)  if(deblocking_filter_override_enabled_flag ) {  pic_deblocking_filter_override_present_flag u(1)   if(pic_deblocking_filter_override_present_flag ) {   pic_deblocking_filter_override_flag u(1)    if(pic_deblocking_filter_override_flag ) {    pic_deblocking_filter_disabled_flag u(1)     if(!pic_deblocking_filter_disabled_flag ) {      pic_beta_offset_div2 se(v)     pic_tc_offset_div2 se(v)     }    }   }  }  if(sps_lmcs_enabled_flag ) {   pic_lmcs_enabled_flag u(1)   if(pic_lmcs_enabled_flag ) {    pic_lmcs_aps_id u(2)    if( ChromaArrayType!= 0 )     pic_chroma_residual_scale_flag u(1)   }  }  if(sps_scaling_list_enabled_flag ) {   pic_scaling_list_present_flag u(1)  if( pic_scaling_list_present_flag )    pic_scaling_list_aps_id u(3)  } if( picture_header_extension_present_flag ) {   ph_extension_lengthue(v)   for( i = 0; i < ph_extension_length; i++ )   ph_extension_data_byte[ i ] u(8)  }  rbsp_trailing_bits( ) }subpics_present_flag equal to 1 indicates tat subpicture parameters arepresent in the present in the SPS RBSP syntax. subpics_present_flagequal to 0 indicates tat subpicture parameters are not present in thepresent in the SPS RBSP syntax.

-   -   NOTE 2—When a bitstream is the result of a sub-bitstream        extraction process and contains only a subset of the subpictures        of the input bitstream to the sub-bitstream extraction process,        it might be required to set the value of subpics_present_flag        equal to 1 in the RBSP of the SPSs.        sps_num_subpics_minus1 plus 1 specifies the number of        subpictures. sps_num_subpics_minus1 shall be in the range of 0        to 254. When not present, the value of sps_num_subpics_minus1 is        inferred to be equal to 0.        subpic_ctu_top_left_x[i] specifies horizontal position of top        left CTU of i-th subpicture in unit of CtbSizeY. The length of        the syntax element is        bits. When not present, the value of subpic_ctu_top_left_x[i] is        inferred to be equal to 0.        subpic_ctu_top_left_y[i] specifies vertical position of top left        CTU of i-th subpicture in unit of CtbSizeY. The length of the        syntax element is        bits. When not present, the value of subpic_ctu_top_left_y[i] is        inferred to be equal to 0.        subpic_width_minus1[i] plus 1 specifies the width of the i-th        subpicture in units of CtbSizeY. The length of the syntax        element is Ceil(Log 2(pic_width_max_in_luma_samples/CtbSizeY)).        When not present, the value of subpic_width_minus1[i] is        inferred to be equal to        −1.        subpic_height_minus1[i] plus 1 specifies the height of the i-th        subpicture in units of CtbSizeY. The length of the syntax        element is Ceil(Log        2(pic_height_max_in_luma_samples/CtbSizeY))bits. When not        present, the value of subpic_height_minus1[i] is inferred to be        equal to        −1.        subpic_treated_as_pic_flag[i] equal to 1 specifies that the i-th        subpicture of each coded picture in the CVS is treated as a        picture in the decoding process excluding in-loop filtering        operations. subpic_treated_as_pic_flag[i] equal to 0 specifies        that the i-th subpicture of each coded picture in the CVS is not        treated as a picture in the decoding process excluding in-loop        filtering operations. When not present, the value of        subpic_treated_as_pic_flag[i] is inferred to be equal to 0.        loop_filter_across_subpic_enabled_flag[i] equal to 1 specifies        that in-loop filtering operations may be performed across the        boundaries of the i-th subpicture in each coded picture in the        CVS.        loop_filter_across_subpic_enabled_flag[i] equal to 0 specifies        that in-loop filtering operations are not performed across the        boundaries of the i-th subpicture in each coded picture in the        CVS. When not present, the value of        loop_filter_across_subpic_enabled_pic_flag[i] is inferred to be        equal to 1.        It is a requirement of bitstream conformance that the following        constraints apply:    -   For any two subpictures subpicA and subpicB, when the index of        subpicA is less than the index of subpicB, any coded NAL unit of        subPicA shall succeed any coded NAL unit of subPicB in decoding        order.    -   The shapes of the subpictures shall be such that each        subpicture, when decoded, shall have its entire left boundary        and entire top boundary consisting of picture boundaries or        consisting of boundaries of previously decoded subpictures.        sps_subpic_id_present_flag equal to 1 specifies that subpicture        Id mapping is present in the SPS. sps_subpic_id_present_flag        equal to 0 specifies that subpicture Id mapping is not present        in the SPS.        sps_subpic_id_signalling_present_flag equal to 1 specifies that        subpicture Id mapping is signalled in the SPS.        sps_subpic_id_signalling_present_flag equal to 0 specifies that        subpicture Id mapping is not signalled in the SPS. When not        present, the value of sps_subpic_id_signalling_present_flag is        inferred to be equal to 0.        sps_subpic_id_len_minus1 plus 1 specifies the number of bits        used to represent the syntax element sps_subpic_id[i]. The value        of sps_subpic_id_len_minus1 shall be in the range of 0 to 15,        inclusive.        sps_subpic_id[i] specifies that subpicture Id of the i-th        subpicture. The length of the sps_subpic_id[i] syntax element is        sps_subpic_id_len_minus1+1 bits. When not present, and when        sps_subpic_id_present_flag equal to 0, the value of        sps_subpic_id[i] is inferred to be equal to i, for each i in the        range of 0 to sps_num_subpics_minus1, inclusive        ph_pic_parameter_set_id specifies the value of        pps_pic_parameter_set_id for the PPS in use. The value of        ph_pic_parameter_set_id shall be in the range of 0 to 63,        inclusive.        It is a requirement of bitstream conformance that the value of        TemporalId of the picture header shall be greater than or equal        to the value of TemporalId of the PPS that has        pps_pic_parameter_set_id equal to ph_pic_parameter_set_id.        ph_subpic_id_signalling_present_flag equal to 1 specifies that        subpicture Id mapping is signalled in the picture header.        ph_subpic_id_signalling_present_flag equal to 0 specifies that        subpicture Id mapping is not signalled in the picture header.        ph_subpic_id_len_minus1 plus 1 specifies the number of bits used        to represent the syntax element ph_subpic_id[i]. The value of        pic_subpic_id_len_minus1 shall be in the range of 0 to 15,        inclusive.        It is a requirement of bitstream conformance that the value of        ph_subpic_id_len_minus1 shall be the same for all picture        headers that are referred to by coded pictures in a CVS.        ph_subpic_id[i] specifies that subpicture Id of the i-th        subpicture. The length of the ph_subpic_id[i] syntax element is        ph_subpic_id_len_minus1+1 bits.        The list SubpicIdList[i] is derived as follows:

 for( i = 0; i <= sps_num_subpics_minus1; i++ )   SubpicIdList[ i ] =sps_subpic_id_present_flag ? (7-39)   ( sps_subpic_id_signalling_present_flag ? sps_subpic_id[ i ] :    (ph_subpic_id_signalling_present_flag ? ph_subpic_id[ i ] :pps_subpic_id[ i] ) ) : i Deblocking filter process

General

Inputs to this process are the reconstructed picture prior todeblocking, i.e., the array recPicture_(L) and, when ChromaArrayType isnot equal to 0, the arrays recPicture_(Cb) and recPicture_(Cr).Outputs of this process are the modified reconstructed picture afterdeblocking, i.e., the array recPicture_(L) and, when ChromaArrayType isnot equal to 0, the arrays recPicture_(Cb) and recPicture_(Cr).The vertical edges in a picture are filtered first. Then the horizontaledges in a picture are filtered with samples modified by the verticaledge filtering process as input. The vertical and horizontal edges inthe CTBs of each CTU are processed separately on a coding unit basis.The vertical edges of the coding blocks in a coding unit are filteredstarting with the edge on the left-hand side of the coding blocksproceeding through the edges towards the right-hand side of the codingblocks in their geometrical order. The horizontal edges of the codingblocks in a coding unit are filtered starting with the edge on the topof the coding blocks proceeding through the edges towards the bottom ofthe coding blocks in their geometrical order.

-   -   NOTE—Although the filtering process is specified on a picture        basis in this Specification, the filtering process can be        implemented on a coding unit basis with an equivalent result,        provided the decoder properly accounts for the processing        dependency order so as to produce the same output values.        The deblocking filter process is applied to all coding subblock        edges and transform block edges of a picture, except the        following types of edges:

    -   Edges that are at the boundary of the picture,

    -   

    -   Edges that coincide with the virtual boundaries of the picture        when pps_loop_filter_across_virtual_boundaries_disabled_flag is        equal to 1,

    -   Edges that coincide with tile boundaries when        loop_filter_across_tiles_enabled_flag is equal to 0,

    -   Edges that coincide with slice boundaries when        loop_filter_across_slices_enabled_flag is equal to 0,

    -   Edges that coincide with upper or left boundaries of slices with        slice_deblocking_filter_disabled_flag equal to 1,

    -   Edges within slices with slice_deblocking_filter_disabled_flag        equal to 1,

    -   Edges that do not correspond to 4×4 sample grid boundaries of        the luma component,

    -   Edges that do not correspond to 8×8 sample grid boundaries of        the chroma component,

    -   Edges within the luma component for which both sides of the edge        have intra_bdpcm_luma_flag equal to 1,

    -   Edges within the chroma components for which both sides of the        edge have intra_bdpcm_chroma_flag equal to 1,

    -   Edges of chroma subblocks that are not edges of the associated        transform unit.        . . .

Deblocking Filter Process for One Direction

Inputs to this process are:

-   -   the variable treeType specifying whether the luma        (DUAL_TREE_LUMA) or chroma components (DUAL_TREE_CHROMA) are        currently processed,    -   when treeType is equal to DUAL_TREE_LUMA, the reconstructed        picture prior to deblocking, i.e., the array recPicture_(L),    -   when ChromaArrayType is not equal to 0 and treeType is equal to        DUAL_TREE_CHROMA, the arrays recPicture_(Cb) and        recPicture_(Cr),    -   a variable edgeType specifying whether a vertical (EDGE_VER) or        a horizontal (EDGE_HOR) edge is filtered.        Outputs of this process are the modified reconstructed picture        after deblocking, i.e:    -   when treeType is equal to DUAL_TREE_LUMA, the array        recPicture_(L),    -   when ChromaArrayType is not equal to 0 and treeType is equal to        DUAL_TREE_CHROMA, the arrays recPicture_(Cb) and        recPicture_(Cr).        The variables firstCompIdx and lastCompIdx are derived as        follows:

firstCompIdx=(treeType==DUAL_TREE_CHROMA)?1:0  (8-1010)

lastCompIdx=(treeType==DUAL_TREE_LUMA|ChromaArrayType==0)?0:2  (8-1011)

For each coding unit and each coding block per colour component of acoding unit indicated by the colour component index cIdx ranging fromfirstCompIdx to lastCompIdx, inclusive, with coding block width nCbW,coding block height nCbH and location of top-left sample of the codingblock (xCb, yCb), when cIdx is equal to 0, or when cIdx is not equal to0 and edgeType is equal to EDGE_VER and xCb % 8 is equal 0, or when cIdxis not equal to 0 and edgeType is equal to EDGE_HOR and yCb % 8 is equalto 0, the edges are filtered by the following ordered steps:

-   -   1. The variable filterEdgeFlag is derived as follows:        -   If edgeType is equal to EDGE_VER and one or more of the            following conditions are true, filterEdgeFlag is set equal            to 0:            -   The left boundary of the current coding block is the                left boundary of the picture.

            -   

            -   The left boundary of the current coding block is the                left boundary of the tile and                loop_filter_across_tiles_enabled_flag is equal to 0.

            -   The left boundary of the current coding block is the                left boundary of the slice and                loop_filter_across_slices_enabled_flag is equal to 0.

            -   The left boundary of the current coding block is one of                the vertical virtual boundaries of the picture and                VirtualBoundariesDisabledFlag is equal to 1.        -   Otherwise, if edgeType is equal to EDGE_HOR and one or more            of the following conditions are true, the variable            filterEdgeFlag is set equal to 0:            -   The top boundary of the current luma coding block is the                top boundary of the picture.

            -   

            -   The top boundary of the current coding lock is the top                boundary of the tile and                loop_filter_across_tiles_enabled_flag is equal to 0.

            -   The top boundary of the current coding block is the top                boundary of the slice and                loop_filter_across_slices_enabled_flag is equal to 0.

            -   The top boundary of the current coding block is one of                the horizontal virtual boundaries of the picture and                VirtualBoundariesDisabledFlag is equal to 1.        -   Otherwise, filterEdgeFlag is set equal to 1.

2.7 Example TPM, HMVP and GEO

Triangular Prediction Mode (TPM) in VVC divides a block into twotriangles with different motion information.

History-based Motion vector Prediction (HMVP) in VVC maintains a tableof motion information to be used for motion vector prediction. The tableis updated after decoding an inter-coded block, but it is not updated ifthe inter-coded block is TPM-coded.

Geometry partition mode (GEO) is an extension of TPM. With GEO, a blockcan be divided by a straight-line into two partitions, which may be ormay not be triangles.

2.8 ALF, CC-ALF and Virtual Boundary

Adaptive Loop-Filter (ALF) in VVC is applied after a picture has beendecoded, to enhance the picture quality.

Virtual Boundary (VB) is adopted in VVC to make ALF friendly to hardwaredesign. With VB, ALF is conducted in an ALF processing unit bounded bytwo ALF virtual boundaries.

Cross-component ALF (CC-ALF) as filters the chroma samples by referringto the information of luma samples.

3. Examples of Technical Problems Solved by Disclosed Embodiments

-   -   (1) There are some designs that can violate the sub-picture        constrain.        -   A. TMVP in the affine constructed candidates may fetch a MV            in the collocated picture out of the range of the current            sub-picture.        -   B. When deriving gradients in Bi-Directional Optical Flow            (BDOF) and Prediction Refinement Optical Flow (PROF), two            extended rows and two extended columns of integer reference            samples are required to be fetched. These reference samples            may be out of the range of the current sub-picture.        -   C. When deriving the chroma residual scaling factor in luma            mapping chroma scaling (LMCS), the accessed reconstructed            luma samples may be out of the range of the range of the            current sub-picture.        -   D. The neighboring block may be out of the range of the            current sub-picture, when deriving the luma intra prediction            mode, reference samples for intra prediction, reference            samples for cross component linear model (CCLM), neighboring            block availability for spatial neighboring candidates for            merge/AMVP/CIIP/IBC/LMCS, quantization parameters,            context-based adaptive binary arithmetic coding (CABAC)            initialization process, ctxInc derivation using left and            above syntax elements, and ctxIncfor the syntax element            mtt_split_cu_vertical_flag. The representation of            sub-picture may lead to sub-picture with incomplete CTUs.            The CTU partitions and coding unit (CU) splitting process            may need to consider incomplete CTUs.    -   (2) The signaled syntax elements related to sub-picture may be        arbitrarily large, which may cause an overflow problem.    -   (3) The representation of sub-pictures may lead to        non-rectangular sub-pictures.    -   (4) Currently the sub-picture and sub-picture grid is defined in        units of 4 samples. And the length of syntax element is        dependent on the picture height divided by 4. However, since the        current pic_width_in_luma_samples and pic_height_in_luma_samples        shall be an integer multiple of Max(8, MinCbSizeY), the        sub-picture grid may need to be defined in units of 8 samples.    -   (5) The SPS syntax, pic_width_max_in_luma_samples and        pic_height_max_in_luma_samples may need to be restricted to be        no smaller than 8.    -   (6) Interaction between reference picture resampling/scalability        and sub-picture is not considered in the current design.    -   (7) In temporal filtering, samples across different sub-pictures        may be required.    -   (8) When signaling the slices, the information could be inferred        without signaling in some cases.    -   (9) It is possible that all the defined slices cannot cover the        whole picture or sub-picture.    -   (1) The IDs of two sub-pictures may be identical.    -   (11) pic_width_max_in_luma_samples/CtbSizeY may be equal to 0,        resulting in a meaningless Log 2( ) operation.    -   (12) ID in picture header (PH) is more preferable than in PPS,        but less preferable than in SPS, which is inconsistent.    -   (13) log 2_transform_skip_max_size_minus2 in PPS is parsed        depending on sps_transform_skip_enabled_flag in SPS, resulting        in a parsing dependency.    -   (14) loop_filter_across_subpic_enabled_flag for deblocking only        consider the current sub-picture, without considering the        neighbouring sub-picture.

4. Example Techniques and Embodiments

The detailed listing below should be considered as examples to explaingeneral concepts. These items should not be interpreted in a narrow way.Furthermore, these items can be combined in any manner. Hereinafter,temporal filter is used to represent filters that require samples inother pictures. Max(x, y) returns the larger one of x and y. Min(x, y)returns the smaller one of x and y.

-   -   1. The position (named position RB) at which a temporal MV        predictor is fetched in a picture to generate affine motion        candidates (e.g. a constructed affine merge candidate) must be        in a required sub-picture, assuming the top-left corner        coordinate of the required sub-picture is (xTL, yTL) and        bottom-right coordinate of the required sub-picture is (xBR,        yBR).        -   a. In one example, the required sub-picture is the            sub-picture covering the current block.        -   b. In one example, if position RB with a coordinate (x, y)            is out of the required sub-picture, the temporal MV            predictor is treated as unavailable.            -   i. In one example, position RB is out of the required                sub-picture if x>xBR.            -   ii. In one example, position RB is out of the required                sub-picture if y>yBR.            -   iii. In one example, position RB is out of the required                sub-picture if x<xTL.            -   iv. In one example, position RB is out of the required                sub-picture if y<yTL.        -   c. In one example, position RB, if outside of the required            sub-picture, a replacement of RB is utilized.            -   i. Alternatively, furthermore, the replacement position                shall be in the required sub-picture.        -   d. In one example, position RB is clipped to be in the            required sub-picture.            -   i. In one example, x is clipped as x=Min(x, xBR).            -   ii. In one example, y is clipped as y=Min(y, yBR).            -   iii. In one example, x is clipped as x=Max(x, xTL).            -   iv. In one example, y is clipped as y=Max(y, yTL).        -   e. In one example, the position RB may be the bottom right            position inside the corresponding block of current block in            the collocated picture.        -   f. The proposed method may be utilized in other coding tools            which require to access motion information from a picture            different than the current picture.        -   g. In one example, whether the above methods are applied            (e.g., position RB must be in a required sub-picture (e.g.            to do as claimed in 1.a and/or 1.b)) may depend on one or            more syntax elements signaled in video parameter set            (VPS)/DPS/SPS/PPS/APS/slice header/tile group header. For            example, the syntax element may be            subpic_treated_as_pic_flag[SubPicIdx], where SubPicIdx is            the sub-picture index of sub-picture covering the current            block.    -   2. The position (named position S) at which an integer sample is        fetched in a reference not used in the interpolation process        must be in a required sub-picture, assuming the top-left corner        coordinate of the required sub-picture is (xTL, yTL) and the        bottom-right coordinate of the required sub-picture is (xBR,        yBR).        -   a. In one example, the required sub-picture is the            sub-picture covering the current block.        -   b. In one example, if position S with a coordinate (x, y) is            out of the required sub-picture, the reference sample is            treated as unavailable.            -   i. In one example, position S is out of the required                sub-picture if x>xBR.            -   ii. In one example, position S is out of the required                sub-picture if y>yBR.            -   iii. In one example, position S is out of the required                sub-picture if x<xTL.            -   iv. In one example, position S is out of the required                sub-picture if y<yTL.        -   c. In one example, position S is clipped to be in the            required sub-picture.            -   i. In one example, x is clipped as x=Min(x, xBR).            -   ii. In one example, y is clipped as y=Min(y, yBR).            -   iii. In one example, x is clipped as x=Max(x, xTL).            -   iv. In one example, y is clipped as y=Max(y, yTL).        -   d. In one example, whether position S must be in a required            sub-picture (e.g. to do as claimed in 2.a and/or 2.b) may            depend on one or more syntax elements signaled in            VPS/dependency parameter set (DPS)/SPS/PPS/adaptation            parameter set (APS)/slice header/tile group header. For            example, the syntax element may be            subpic_treated_as_pic_flag[SubPicIdx], where SubPicIdx is            the sub-picture index of sub-picture covering the current            block.        -   e. In one example, the fetched integer sample is used to            generate gradients in BDOF and/or PROF.    -   3. The position (named position R) at which the reconstructed        luma sample value is fetched may be in a required sub-picture,        assuming the top-left corner coordinate of the required        sub-picture is (xTL, yTL) and the bottom-right coordinate of the        required sub-picture is (xBR, yBR).        -   a. In one example, the required sub-picture is the            sub-picture covering the current block.        -   b. In one example, if position R with a coordinate (x, y) is            out of the required sub-picture, the reference sample is            treated as unavailable.            -   i. In one example, position R is out of the required                sub-picture if x>xBR.            -   ii. In one example, position R is out of the required                sub-picture if y>yBR.            -   iii. In one example, position R is out of the required                sub-picture if x<xTL.            -   iv. In one example, position R is out of the required                sub-picture if y<yTL.        -   c. In one example, position R is clipped to be in the            required sub-picture.            -   i. In one example, x is clipped as x=Min(x, xBR).            -   ii. In one example, y is clipped as y=Min(y, yBR).            -   iii. In one example, x is clipped as x=Max(x, xTL).            -   iv. In one example, y is clipped as y=Max(y, yTL).        -   d. In one example, whether position R must be in a required            sub-picture (e.g. to do as claimed in 4.a and/or 4.b) may            depend on one or more syntax elements signaled in            VPS/DPS/SPS/PPS/APS/slice header/tile group header. For            example, the syntax element may be            subpic_treated_as_pic_flag[SubPicIdx], where SubPicIdx is            the sub-picture index of sub-picture covering the current            block.        -   e. In one example, the fetched luma sample is used to derive            the scaling factor for the chroma component(s) in LMCS.    -   4. The position (named position N) at which the picture boundary        check for binary tree (BT)/triple tree (TT)/quad tree (QT)        splitting, BT/TT/QT depth derivation, and/or the signaling of CU        split flag must be in a required sub-picture, assuming the        top-left corner coordinate of the required sub-picture is (xTL,        yTL) and the bottom-right coordinate of the required sub-picture        is (xBR, yBR).        -   a. In one example, the required sub-picture is the            sub-picture covering the current block.        -   b. In one example, if position N with a coordinate (x, y) is            out of the required sub-picture, the reference sample is            treated as unavailable.            -   i. In one example, position N is out of the required                sub-picture if x>xBR.            -   ii. In one example, position N is out of the required                sub-picture if y>yBR.            -   iii. In one example, position N is out of the required                sub-picture if x<xTL.            -   iv. In one example, position N is out of the required                sub-picture if y<yTL.        -   c. In one example, position N is clipped to be in the            required sub-picture.            -   i. In one example, x is clipped as x=Min(x, xBR).            -   ii. In one example, y is clipped as y=Min(y, yBR).            -   iii. In one example, x is clipped as x=Max(x, xTL).        -   d. In one example, y is clipped as y=Max(y, yTL). In one            example, whether position N must be in a required            sub-picture (e.g. to do as claimed in 5.a and/or 5.b) may            depend on one or more syntax elements signaled in            VPS/DPS/SPS/PPS/APS/slice header/tile group header. For            example, the syntax element may be            subpic_treated_as_pic_flag[SubPicIdx], where SubPicIdx is            the sub-picture index of sub-picture covering the current            block.    -   5. History-based Motion Vector Prediction (HMVP) table may be        reset before decoding a new sub-picture in one picture.        -   a. In one example, the HMVP table used for IBC coding may be            reset        -   b. In one example, the HMVP table used for inter coding may            be reset        -   c. In one example, the HMVP table used for intra coding may            be reset    -   6. The sub-picture syntax elements may be defined in units of N        (such as N=8, 32, and etc) samples.        -   a. In one example, the width of each element of the            sub-picture identifier grid in units of N samples.        -   b. In one example, the height of each element of the            sub-picture identifier grid in units of N samples.        -   c. In one example, N is set to the width and/or height of            CTU.    -   7. The syntax element of picture width and picture height may be        restricted to be no smaller than K (K>=8).        -   a. In one example, the picture width may need to be            restricted to be no smaller than 8.        -   b. In one example, the picture height may need to be            restricted to be no smaller than 8.    -   8. A conformance bitstream shall satisfy that sub-picture coding        and Adaptive resolution conversion (ARC)/Dynamic resolution        conversion (DRC)/Reference picture resampling (RPR) are        disallowed to be enabled for one video unit (e.g., sequence).        -   a. In one example, signaling of enabling sub-picture coding            may be under the conditions of disallowing ARC/DRC/RPR.            -   i. In one example, when sub-picture is enabled, such as                subpics_present_flag equal to 1,                pic_width_in_luma_samples for all pictures for which                this SPS is active is equal to                max_width_in_luma_samples.        -   b. Alternatively, sub-picture coding and ARC/DRC/RPR may be            both enabled for one video unit (e.g., sequence).            -   i. In one example, a conformance bitstream shall satisfy                that the donwsampled sub-picture due to ARC/DRC/RPR                shall still be in the form of K CTUs in width and M CTUs                in height wherein K and M are both integers.            -   ii. In one example, a conformance bitstream shall                satisfy that for sub-pictures not located at picture                boundaries (e.g., right boundary and/or bottom                boundary), the donwsampled sub-picture due to                ARC/DRC/RPR shall still be in the form of K CTUs in                width and M CTUs in height wherein K and M are both                integers.            -   iii. In one example, CTU sizes may be adaptively changed                based on the picture resolution.                -   1) In one example, a max CTU size may be signaled in                    SPS. For each picture with less resolution, the CTU                    size may be changed accordingly based on the reduced                    resolution.                -   2) In one example, CTU size may be signaled in SPS                    and PPS, and/or sub-picture level.    -   9. The syntax element subpic_grid_col_width_minus1 and        subpic_grid_row_height_minus1 may be constrained.        -   a. In one example, subpic_grid_col_width_minus1 must be no            larger (or must be smaller) than T1.        -   b. In one example, subpic_grid_row_height_minus1 must be no            larger (or must be smaller) than T2.        -   c. In one example, in a conformance bit-stream,            subpic_grid_col_width_minus1 and/or            subpic_grid_row_height_minus1 must follow the constraint            such as bullet 3.a or 3.b.        -   d. In one example, T1 in 3.a and/or T2 in 3.b may depend on            profiles/levels/tiers of a video coding standard.        -   e. In one example, T1 in 3.a may depend on the picture            width.            -   i. For example, T1 is equal to                pic_width_max_in_luma_samples/4 or                pic_width_max_in_luma_samples/4+Off. Off may be 1, 2,                −1, −2, etc.        -   f. In one example, T2 in 3.b may depend on the picture            width.            -   i. For example, T2 is equal to                pic_height_max_in_luma_samples/4 or                pic_height_max_in_luma_samples/4-1+Off. Off may be 1, 2,                −1, −2, etc.    -   10. It is constrained that a boundary between two sub-pictures        must be a boundary between two CTUs.        -   a. In other words, a CTU cannot be covered by more than one            sub-picture.        -   b. In one example, the unit of subpic_grid_col_width_minus1            may be the CTU width (such as 32, 64, 128), instead of 4 as            in VVC. The sub-picture grid width should be            (subpic_grid_col_width_minus1+1)*CTU width.        -   c. In one example, the unit of subpic_grid_col_height_minus1            may be the CTU height (such as 32, 64, 128), instead of 4 as            in VVC. The sub-picture grid height should be            (subpic_grid_col_height_minus1+1)*CTU height.        -   d. In one example, in a conformance bit-stream, the            constraint must be satisfied if the sub-picture approach is            applied.    -   11. It is constrained that the shape of a sub-picture must be        rectangular.        -   a. In one example, in a conformance bit-stream, the            constraint must be satisfied if the sub-picture approach is            applied.        -   b. Sub-picture may only contain rectangular slices. For            example, in a conformance bit-stream, the constraint must be            satisfied if the sub-picture approach is applied.    -   12. It is constrained that two sub-pictures cannot be        overlapped.        -   a. In one example, in a conformance bit-stream, the            constraint must be satisfied if the sub-picture approach is            applied.        -   b. Alternatively, two sub-pictures may be overlapped with            each other.    -   13. It is constrained that any position in the picture must be        covered by one and only one sub-picture.        -   a. In one example, in a conformance bit-stream, the            constraint must be satisfied if the sub-picture approach is            applied.        -   b. Alternatively, one sample may not belong to any            sub-picture.        -   c. Alternatively, one sample may belong to more than one            sub-pictures.    -   14. It may be constrained that sub-pictures defined in a SPS        mapped to every resolution presented in the same sequence should        obey the location and/or size constrained mentioned above.        -   a. In one example, the width and height of a sub-picture            defined in the SPS mapped to a resolution presented in the            same sequence, should be integer multiple times of N (such            as 8, 16, 32) luma samples.        -   b. In one example, sub-pictures maybe defined for certain            layer and maybe mapped to other layers.            -   i. For example, sub-pictures may be defined for the                layer with the highest resolution in the sequence.            -   ii. For example, sub-pictures may be defined for the                layer with the lowest resolution in the sequence.            -   iii. Which layer the sub-pictures are defined for may be                signaled in SPS/VPS/PPS/slice header.        -   c. In one example, when sub-pictures and different            resolutions are both applied, all resolutions (e.g., width            or/and height) may be integer multiple of a given            resolution.        -   d. In one example, the width and/or height of a sub-picture            defined in the SPS may be integer multiple times (e.g., M)            of the CTU size.        -   e. Alternatively, sub-pictures and different resolutions in            a sequence may not be allowed simultaneously.    -   15. Sub-pictures may only apply to a certain layer(s)        -   a. In one example, sub-pictures defined in a SPS may only            apply to the layer with the highest resolution in a            sequence.        -   b. In one example, sub-pictures defined in a SPS may only            apply to the layer with the lowest temporal id in a            sequence.        -   c. Which layer(s) that sub-pictures may be applied to may be            indicated by one or multiple syntax elements in SPS/VPS/PPS.        -   d. Which layer(s) that sub-picture cannot be applied to may            be indicated by one or multiple syntax elements in            SPS/VPS/PPS.    -   16. In one example, the position and/or dimensions of a        sub-picture may be signaled without using subpic_grid_idx.        -   a. In one example, the top-left position of a sub-picture            may be signaled.        -   b. In one example, the bottom-right position of a            sub-picture may be signaled.        -   c. In one example, the width of sub-picture may be signaled.        -   d. In one example, the height of a sub-picture may be            signaled.    -   17. For temporal filter, when performing the temporal filtering        of a sample, only samples within the same sub-picture that the        current sample belongs to may be used. The required samples may        be in the same picture that the current sample belongs to or in        other pictures.    -   18. In one example, whether to and/or how to apply a        partitioning method (such as QT, horizontal BT, vertical BT,        horizontal TT, vertical TT, or not split, etc.) may depend on        whether the current block (or partition) crosses one or multiple        boundary of a sub-picture.        -   a. In one example, the picture boundary handling method for            partitioning in VVC may also be applied when a picture            boundary is replaced by a sub-picture boundary.        -   b. In one example, whether to parse a syntax element (e.g. a            flag) which represents a partitioning method (such as QT,            horizontal BT, vertical BT, horizontal TT, vertical TT, or            not split, etc.) may depend on whether the current block (or            partition) crosses one or multiple boundary of a            sub-picture.    -   19. Instead of splitting one picture into multiple sub-pictures        with independent coding of each sub-picture, it is proposed to        split a picture into at least two sets of sub-regions, with the        first set including multiple sub-pictures and the second set        including all the remaining samples.        -   a. In one example, a sample in the second set is not in any            sub-pictures.        -   b. Alternatively, furthermore, the second set may be            encoded/decoded based on the information of the first set.        -   c. In one example, a default value may be utilized to mark            whether a sample/M×K sub-region belonging to the second set.            -   i. In one example, the default value may be set equal to                (max_subpics_minus1+K) wherein K is an integer greater                than 1.            -   ii. The default value maybe assigned to                subpic_grid_idx[i][j] to indicate that grid belongs to                the second set.    -   20. It is proposed that the syntax element subpic_grid_idx[i][j]        cannot be larger than max_subpics_minus1.        -   a. For example, it is constrained that in a conformance            bit-stream, subpic_grid_idx[i][j] cannot be larger than            max_subpics_minus1.        -   b. For example, the codeword to code subpic_grid_idx[i][j]            cannot be larger than max_subpics_minus1.    -   21. It is proposed that, any integer number from 0 to        max_subpics_minus1 must be equal to at least one        subpic_grid_idx[i][j].    -   22. IBC virtual buffer may be reset before decoding a new        sub-picture in one picture.        -   a. In one example, all the samples in the IBC virtual buffer            may be reset to −1.    -   23. Palette entry list may be reset before decoding a new        sub-picture in one picture.        -   a. In one example, PredictorPaletteSize may be set equal to            0 before decoding a new sub-picture in one picture.    -   24. Whether to signal the information of slices (e.g. number of        slices and/or ranges of slices) may depend on the number of        tiles and/or the number of bricks.        -   a. In one example, if the number of bricks in a picture is            one, num_slice_sin_pic_minus1 is not signaled and inferred            to be 0.        -   b. In one example, if the number of bricks in a picture is            one, the information of slices (e.g. number of slices and/or            ranges of slices) may not be signaled.        -   c. In one example, if the number of bricks in a picture is            one, the number of slices may be inferred to be one. And the            slice covers the whole picture. In one example, if the            number of bricks in a picture is one,            single_brick_per_slice_flag is not signaled and inferred to            be one.            -   i. Alternatively, if the number of bricks in a picture                is one, single_brick_per_slice_flag must be one.        -   d. An exemplary syntax design is as below:

Descriptor pic_parameter_set_rbsp( ) { ...  

  single_brick_per_slice_flag u(1)   if( !single_brick_per_slice_flag )   rect_slice_flag u(1)   if( rect_slice_flag &&!single_brick_per_slice_flag ) {    num_slices_in_pic_minus1 ue(v)   bottom_right_brick_idx_length_minus1 ue(v)    for( i = 0; i <num_slices_in_pic_minus1; i++ ) {     bottom_right_brick_idx_delta[ i ]u(v)     brick_idx_delta_sign_flag[ i ] u(1)    }   }  

  loop_filter_across_bricks_enabled_flag u(1)   if(loop_filter_across_bricks_enabled_flag )   loop_filter_across_slices_enabled_flag u(1)  } ...

-   -   25. Whether to signal slice_address may be decoupled from        whether slices are signaled to be rectangles (e.g. whether        rect_slice_flag is equal to 0 or 1).        -   a. An exemplary syntax design is as below:

if( [[rect_slice_flag ∥]] NumBricksInPic > 1 )  slice_address u(v)

-   -   26. Whether to signal slice_address may depend on the number of        slices when slices are signaled to be rectangles.

 if(( rect_slice_flag && num_slices_in_pic_minus1> 0) ∥(!rect_slice_flag && NumBricksInPic > 1 ))   slice_address u(v)

-   -   27. Whether to signal num_bricks_in_slice_minus1 may depend on        the slice_address and/or the number of bricks in the picture.        -   a. An exemplary syntax design is as below:

if( !rect_slice_flag && !single_brick_per_slice_flag

 < 

num_bricks_in_slice_minus1 ue(v)

-   -   28. Whether to signal loop_filter_across_bricks_enabled_flag may        depend on the number of tiles and/or the number of bricks.        -   a. In one example, loop_filter_across_bricks_enabled_flag is            not signaled if the number of bricks is less than 2.        -   b. An exemplary syntax design is as below:

Descriptor pic_parameter_set_rbsp( ) { ...  

  loop_filter_across_bricks_enabled_flag u(1)   if(loop_filter_across_bricks_enabled_flag )   loop_filter_across_slices_enabled_flag u(1) ...

-   -   29. It is a requirement of bitstream conformance that all the        slices of a picture must cover the whole picture.        -   a. The requirement must be satisfied when slices are            signaled to be rectangles (e.g. rect_slice_flag is equal to            1).    -   30. It is a requirement of bitstream conformance that all the        slices of a sub-picture must cover the whole sub-picture.        -   a. The requirement must be satisfied when slices are            signaled to be rectangles (e.g. rect_slice_flag is equal to            1).    -   31. It is a requirement of bitstream conformance that a slice        cannot be overlapped with more than one sub-picture.    -   32. It is a requirement of bitstream conformance that a tile        cannot be overlapped with more than one sub-picture.    -   33. It is a requirement of bitstream conformance that a brick        cannot be overlapped with more than one sub-picture.        -   In the following discussion, a basic unit block (BUB) with            dimensions CW×CH is a rectangle region. For example, a BUB            may be a Coding Tree Block (CTB).    -   34. In one example, the number of sub-pictures (denoted as N)        may be signaled.        -   a. It may be required on a conformance bit-stream that there            are at least two sub-pictures in a picture if sub-pictures            are used (e.g. subpics_present_flag is equal to 1).        -   b. Alternatively, N minus d (i.e., N−d) may be signaled,            where d is an integer such as 0, 1, or 2.        -   c. For example, N−d may be coded with fixed length coding            e.g. u(x).            -   i. In one example, x may be a fixed number such as 8.            -   ii. In one example, x or x-dx may be signaled before N−d                is signaled, where dx is an integer such as 0, 1 or 2.                The signaled x may not be larger than a maximum value in                a conformance bitstream.            -   iii. In one example, x may be derived on-the-fly.                -   1) For example, x may be derived as a function of                    the total number (denoted as M) of BUBs in the                    picture. E.g., x=Ceil(log 2(M+d0))+d1, where d0 and                    d1 are two integers, such as −2, −1, 0, 1, 2, etc.                    Here, Ceil( ) function returns the smallest integer                    value that is bigger than or equal to the input                    value.                -   2) M may be derived as                    M=Ceiling(W/CW)×Ceiling(H/CH), where W and H                    represent the width and height of the picture, and                    CW and CH represent the width and height of a BUB.        -   d. For example, N−d may be coded with a unary code or a            truncated unary code.        -   e. In one example, the allowed maximum value of N−d may be a            fixed number.            -   i. Alternatively, the allowed maximum value of N−d may                be derived as a function of the total number (denoted                as M) of BUBs in the picture. E.g., x=Ceil(log                2(M+d0))+d1, where d0 and d1 are two integers, such as                −2, −1, 0, 1, 2, etc. Here, Ceil(function returns the                smallest integer value that is bigger than or equal to                the input value.    -   35. In one example, a sub-picture may be signaled by indications        of one or multiple its selected positions (e.g.,        top-left/top-right/bottom-left/bottom-right position) and/or its        width and/or its height.        -   a. In one example, the top-left position of a sub-picture            may be signaled in the granularity of a basic unit block            (BUB) with dimensions CW×CH.            -   i. For example, the column index (denoted as Col) in                terms of BUBs of the top-left BUB of the sub-picture may                be signaled.                -   1) For example, Col−d may be signaled, where d is an                    integer such as 0, 1, or 2.                -    a) Alternatively, d may be equal to Col of a                    sub-picture previously coded, added by d1, where d1                    is an integer such as −1, 0, or 1.                -    b) The sign of Col−d may be signaled.            -   ii. For example, the row index (denoted as Row) in term                of BUBs of the top-left BUB of the sub-picture may be                signaled.                -   1) For example, Row−d may be signaled, where d is an                    integer such as 0, 1, or 2.                -    a) Alternatively, d may be equal to Row of a                    sub-picture previously coded, added by d1, where d1                    is an integer such as −1, 0, or 1.                -    b) The sign of Row −d may be signaled.            -   iii. The row/column index (denoted as Row) mentioned                above may be represented in the Coding Tree Block (CTB)                unit, e.g., the x or y coordinate relative to the                top-left position of a picture may be divided by CTB                size and signaled.            -   iv. In one example, whether to signal the position of a                sub-picture may depend on the sub-picture index.                -   1) In one example, for the first sub-picture within                    a picture, the top-left position may be not                    signaled.                -    a) Alternatively, furthermore, the top-left                    position may be inferred, e.g., to be (0, 0).                -   2) In one example, for the last sub-picture within a                    picture, the top-left position may be not signaled.                -    a) The top-left position may be inferred depending                    on information of sub-pictures previously signaled.        -   b. In one example, indications of the width/height/a            selected position of a sub-picture may be signaled with            truncated unary/truncated binary/unary/fixed length/K-th            Exponential-Golomb (OEG) coding (e.g., K=0, 1, 2, 3).        -   c. In one example, the width of a sub-picture may be            signaled in the granularity of a BUB with dimensions CW×CH.            -   i. For example, the number of columns of BUBs in the                sub-picture (denoted as W) may be signaled.            -   ii. For example, W-d may be signaled, where d is an                integer such as 0, 1, or 2.                -   1) Alternatively, d may be equal to W of a                    sub-picture previously coded, added by d1, where d1                    is an integer such as −1,0, or 1.                -   2) The sign of W-d may be signaled.        -   d. In one example, the height of a sub-picture may be            signaled in the granularity of a BUB with dimensions CW×CH.            -   i. For example, the number of rows of BUBs in the                sub-picture (denoted as H) may be signaled.            -   ii. For example, H-d may be signaled, where d is an                integer such as 0, 1, or 2.                -   1) Alternatively, d may be equal to H of a                    sub-picture previously coded, added by d1, where d1                    is an integer such as −1,0, or 1.                -   2) The sign of H-d may be signaled.        -   e. In one example, Col-d may be coded with fixed length            coding e.g. u(x).            -   i. In one example, x may be a fixed number such as 8.            -   ii. In on example, x or x-dx may be signaled before                Col-d is signaled, where dx is an integer such as 0, 1                or 2. The signaled x may not be larger than a maximum                value in a conformance bitstream.            -   iii. In one example, x may be derived on-the-fly.                -   1) For example, x may be derived as a function of                    the total number (denoted as M) of BUB columns in                    the picture. E.g., x=Ceil(log 2(M+d0))+d1, where d0                    and d1 are two integers, such as −2, −1, 0, 1, 2,                    etc. Here, Ceil( ) function returns the smallest                    integer value that is bigger than or equal to the                    input value.                -   2) M may be derived as M=Ceiling(W/CW), where W                    represents the width of the picture, and CW                    represents the width of a BUB.        -   f. In one example, Row-d may be coded with fixed length            coding e.g. u(x).            -   i. In one example, x may be a fixed number such as 8.            -   ii. In one example, x or x-dx may be signaled before                Row-d is signaled, where dx is an integer such as 0, 1                or 2. The signaled x may not be larger than a maximum                value in a conformance bitstream.            -   iii. In one example, x may be derived on-the-fly.                -   1) For example, x may be derived as a function of                    the total number (denoted as M) of BUB rows in the                    picture. E.g., x=Ceil(log 2(M+d0))+d1, where d0 and                    d1 are two integers, such as −2, −1, 0, 1, 2, etc.                    Here, Ceil( ) function returns the smallest integer                    value that is bigger than or equal to the input                    value.                -   2) M may be derived as M=Ceiling(H/CH), where H                    represents the height of the picture, and CH                    represents the height of a BUB.        -   g. In one example, W-d may be coded with fixed length coding            e.g. u(x).            -   i. In one example, x may be a fixed number such as 8.            -   ii. In on example, x or x-dx may be signaled before W-d                is signaled, where dx is an integer such as 0, 1 or 2.                The signaled x may not be larger than a maximum value in                a conformance bitstream.            -   iii. In one example, x may be derived on-the-fly.                -   1) For example, x may be derived as a function of                    the total number (denoted as M) of BUB columns in                    the picture. E.g., x=Ceil(log 2(M+d0))+d1, where d0                    and d1 are two integers, such as −2, −1, 0, 1, 2,                    etc. Here, Ceil( ) function returns the smallest                    integer value that is bigger than or equal to the                    input value.                -   2) M may be derived as M=Ceiling(W/CW), where W                    represents the width of the picture, and CW                    represents the width of a BUB.        -   h. In one example, H-d may be coded with fixed length coding            e.g. u(x).            -   i. In one example, x may be a fixed number such as 8.            -   ii. In one example, x or x-dx may be signaled before H-d                is signaled, where dx is an integer such as 0, 1 or 2.                The signaled x may not be larger than a maximum value in                a conformance bitstream.            -   iii. In one example, x may be derived on-the-fly.                -   1) For example, x may be derived as a function of                    the total number (denoted as M) of BUB rows in the                    picture. E.g., x=Ceil(log 2(M+d0))+d1, where d0 and                    d1 are two integers, such as −2, −1, 0, 1, 2, etc.                    Here, Ceil( ) function returns the smallest integer                    value that is bigger than or equal to the input                    value.                -   2) M may be derived as M=Ceiling(H/CH), where H                    represents the height of the picture, and CH                    represents the height of a BUB.        -   i. Col-d and/or Row-d may be signaled for all sub-pictures.            -   i. Alternatively, Col-d and/or Row-d may not be signaled                for all sub-pictures.                -   1) Col-d and/or Row-d may not be signaled if the                    number of sub-pictures are less than 2. (equal to                    1).                -   2) For example, Col-d and/or Row-d may not be                    signaled for the first sub-picture (e.g. with the                    sub-picture index (or sub-picture ID) equal to 0).                -    a) When they are not signaled, they may be inferred                    to be 0.                -   3) For example, Col-d and/or Row-d may not be                    signaled for the last sub-picture (e.g. with the                    sub-picture index (or sub-picture ID) equal to                    NumSubPics−1).                -    a) When they are not signaled, they may be inferred                    depending on the positions and dimensions of                    sub-pictures already signaled.        -   j. W-d and/or H-d may be signaled for all sub-pictures.            -   i. Alternatively, W-d and/or H-d may not be signaled for                all sub-pictures.                -   1) W-d and/or H-d may not be signaled if the number                    of sub-pictures are less than 2. (equal to 1).                -   2) For example, W-d and/or H-d may not be signaled                    for the last sub-picture (e.g. with the sub-picture                    index (or sub-picture ID) equal to NumSubPics−1).                -    a) When they are not signaled, they may be inferred                    depending on the positions and dimensions of                    sub-pictures already signaled.        -   k. In the above bullets, a BUB may be a Coding Tree Block            (CTB).    -   36. In one example, the information of sub-pictures should be        signaled after information of the CTB size (e.g. log        2_ctu_size_minus5) has already been signaled.    -   37. subpic_treated_as_pic_flag[i] may not be signaled for each        sub-pictures. Instead, one subpic_treated_as_pic_flag is        signaled to control whether a sub-picture is treated as a        picture for all sub-pictures.    -   38. loop_filter_across_subpic_enabled_flag [i] may not be        signaled for each sub-pictures. Instead, one        loop_filter_across_subpic_enabled_flag is signaled to control        whether loop filters can be applied across sub-pictures for all        sub-pictures.    -   39. subpic_treated_as_pic_flag[i] (subpic_treated_as_pic_flag)        and/or loop_filter_across_subpic_enabled_flag[i]        (loop_filter_across_subpic_enabled_flag) may be signaled        conditionally.        -   a. In one example, subpic_treated_as_pic_flag[i] and/or            loop_filter_across_subpic_enabled_flag[i] may not be            signaled if the number of sub-pictures are less than 2.            (equal to 1).    -   40. RPR may be applied when sub-pictures are used.        -   a. In one example, the scaling ratio in RPR may be            constrained to be a limited set when sub-pictures are used,            such as {1:1, 1:2 and/or 2:1}, or {1:1, 1:2 and/or 2:1, 1:4            and/or 4:1}, {1:1, 1:2 and/or 2:1, 1:4 and/or 4:1, 1:8            and/or 8:1}.        -   b. In one example, the CTB size of a picture A and the CTB            size of a picture B may be different if the resolution of            picture A and picture B are different.        -   c. In one example, suppose a sub-picture SA with dimensions            SAW×SAH is in picture A and a sub-picture SB with dimensions            SBW×SBH is in picture B, SA corresponds to SB, and the            scaling ratios between picture A and picture B are Rw and Rh            along the horizontal and vertical directions, then            -   i. SAW/SBW or SBW/SAW should be equal to Rw.            -   ii. SAH/SBH or SBH/SAH should be equal to Rh.    -   41. When sub-pictures are used (e.g. sub_pics_present_flag is        true), a subpicture index (or sub-picture ID) may be signaled in        the slice header, and the slice address is interrupted as the        address in a sub-picture instead of the whole picture.    -   42. It is required that the subpicture ID of a first subpicture        must be different to the subpicture ID of a second subpicture,        if the first subpicture and the second subpicture are not the        same sub-picture.        -   a. In one example, it is a requirement in a conformance            bitstream that sps_subpic_id[i] must be different from            sps_subpic_id[j], if i is not equal to j.        -   b. In one example, it is a requirement in a conformance            bitstream that pps_subpic_id[i] must be different from            pps_subpic_id[j], if i is not equal to j.        -   c. In one example, it is a requirement in a conformance            bitstream that ph_subpic_id[i] must be different from            ph_subpic_id[j], if i is not equal to j.        -   d. In one example, it is a requirement in a conformance            bitstream that SubpicIdList[i] must be different from            SubpicIdList[j], if i is not equal to j.        -   e. In one example, a difference denoted as D[i] equal to            X_subpic_id[i]−X_subpic_id[i−P] may be signaled.            -   i. For example, X may be sps, pps or ph.            -   ii. For example, P is equal to 1.            -   iii. For example, i>P.            -   iv. For example, D[i] must be larger than 0.            -   v. For example, D[i]−1 may be signaled.    -   43. It is proposed that the length of a syntax element        specifying the horizontal or vertical position of top left CTU        (e.g. subpic_ctu_top_left_x or subpic_ctu_top_left_y) may be        derived to be Ceil(Log 2(SS)) bits, wherein SS must be larger        than 0. Here, Ceil(function returns the smallest integer value        that is bigger than or equal to the input value.        -   a. In one example,            SS=(pic_width_max_in_luma_samples+RR)/CtbSizeY when the            syntax element specifies the horizontal position of top left            CTU (e.g. subpic_ctu_top_left_x).        -   b. In one example,            SS=(pic_height_max_in_luma_samples+RR)/CtbSizeY when the            syntax element specifies the vertical position of top left            CTU (e.g. subpic_ctu_top_left_y).        -   c. In one example, RR is a non-zero integer such as            CtbSizeY−1.    -   44. It is proposed that the length of a syntax element        specifying the horizontal or vertical position of top left CTU        of a subpicture (e.g. subpic_ctu_top_left_x or        subpic_ctu_top_left_y) may be derived to be Ceil(Log 2(SS))        bits, wherein SS must be larger than 0. Here, Ceil(function        returns the smallest integer value that is bigger than or equal        to the input value.        -   a. In one example,            SS=(pic_width_max_in_luma_samples+RR)/CtbSizeY when the            syntax element specifies the horizontal position of top left            CTU of a subpicture (e.g. subpic_ctu_top_left_x).        -   b. In one example,            SS=(pic_height_max_in_luma_samples+RR)/CtbSizeY when the            syntax element specifies the vertical position of top left            CTU of a subpicture (e.g. subpic_ctu_top_left_y).        -   c. In one example, RR is a non-zero integer such as            CtbSizeY−1.    -   45. It is proposed that the default value of the length of a        syntax element (which may plus an offset P such as 1) specifying        the width or height of a subpicture (e.g. subpic_width_minus1 or        subpic_height_minus1) may be derived to be Ceil(Log 2(SS))−P,        wherein SS must be larger than 0. Here, Ceil(function returns        the smallest integer value that is bigger than or equal to the        input value.        -   a. In one example,            SS=(pic_width_max_in_luma_samples+RR)/CtbSizeY when the            syntax element specifies the default width (which may plus            an offset P) of a subpicture (e.g. subpic_width_minus1).        -   b. In one example,            SS=(pic_height_max_in_luma_samples+RR)/CtbSizeY when the            syntax element specifies the default height (which may plus            an offset P) of a subpicture (e.g. subpic_height_minus1).        -   c. In one example, RR is a non-zero integer such as            CtbSizeY−1.    -   46. It is proposed that, the information of IDs of sub-pictures        should be signaled at least in one of SPS, PPS, and the picture        header if it is determined that the information should be        signaled.        -   a. In one example, it is a requirement in a conformance            bitstream that at least one of            sps_subpic_id_signalling_present_flag,            pps_subpic_id_signalling_present_flag and            ph_subpic_id_signalling_present_flag should be equal to 1 if            sps_subpic_id_present_flag is equal to 1.    -   47. It is proposed that, if the information of IDs of        sub-pictures is not signaled in any one of SPS, PPS, and the        picture header, but it is determined that the information should        be signaled. default IDs should be assigned.        -   a. In one example, if sps_subpic_id_signalling_present_flag,            pps_subpic_id_signalling_present_flag and            ph_subpic_id_signalling_present_flag are all equal to 0 and            sps_subpic_id_present_flag is equal to 1, SubpicIdList[i]            should be set equal to i+P, where P is an offset such as 0.            An exemplary description is as below:

for(i=0;i<=sps_num_subpics_minus1;i++)

SubpicIdList[i]=sps_subpic_id_present_flag?(sps_subpic_id_signalling_present_flag?sps_subpic_id[i]:(ph_subpic_id_signalling_present_flag?ph_subpic_id[i]:

)): i

-   -   48. It is proposed that the information of sub-picture IDs are        not signaled in a picture header if they are signaled in the        corresponding PPS.        -   a. An exemplary syntax design is as below,

Descriptor picture_header_rbsp( ) {  non_reference_picture_flag u(1) gdr_pic_flag u(1)  no_output_of_prior_pics_flag u(1)  if( gdr_pic_flag)   recovery_poc_cnt ue(v)  ph_pic_parameter_set_id ue(v)  if(sps_subpic_id_present_flag &&  !sps_subpic_id_signalling_flag && !pps_subpic_id_signalling_flag) {   ph_subpic_id_signalling_present_flagu(1)   if( ph_subpics_id_signalling_present_flag ) {   ph_subpic_id_len_minus1 ue(v)    for( i = 0; i <=sps_num_subpics_minus1; i++ )     ph_subpic_id[ i ] u(v)   }  }  ...

-   -   -   b. In one example, the sub-picture IDs are set according to            the information of sub-picture IDs signaled in SPS if they            are signaled in SPS; Otherwise, the sub-picture IDs are set            according to the information of sub-picture IDs signaled in            PPS if they are signaled in PPS, Otherwise, the sub-picture            IDs are set according to the information of sub-picture IDs            signaled in the the picture header if they are signaled in            the picture header. An exemplary description is as below,

for(i=0;i<=sps_num_subpics_minus1;i++)

SubpicIdList[i]=sps_subpic_id_present_flag?(sps_subpic_id_signalling_present_flag?sps_subpic_id[i](pps_subpic_id_signalling_present_flag?pps_subpic_id[i]:(ph_subpic_id_signalling_present_flag?ph_subpic_id[i]:i))):i

-   -   -   c. In one example, the sub-picture IDs are set according to            the information of sub-picture IDs signaled in the picture            header if they are signaled in the picture header;            Otherwise, the sub-picture IDs are set according to the            information of sub-picture IDs signaled in PPS if they are            signaled in PPS, Otherwise, the sub-picture IDs are set            according to the information of sub-picture IDs signaled in            the SPS if they are signaled in SPS. An exemplary            description is as below,

for(i=0;i<=sps_num_subpics_minus1;i++)

SubpicIdList[i]=sps_subpic_id_present_flag?(ph_subpic_id_signalling_present_flag?ph_subpic_id[i](pps_subpic_id_signalling_present_flag?pps_subpic_id[i]:(sps_subpic_id_signalling_present_flag?sps_subpic_id[i]: i))): i

-   -   49. It is proposed that the deblocking process on an edge E        should depend on the determination of whether loop-filtering is        allowed across the subpicture boundaries (e.g. determined by        loop_filter_across_subpic_enabled_flag) on both sides (denoted        as P-side and Q-side) of the edge. P-side represents the side in        the current block, and Q-side represents the side in the        neighbouring block, which may belong to a different sub-picture.        In the following discussion, it is assumed that P-side and        Q-side belongs two different sub-pictures.        loop_filter_across_subpic_enabled_flag[P]=0/1 means that        loop-filtering is disallowed/allowed across the subpicture        boundaries of the subpicture containing P-side.        loop_filter_across_subpic_enabled_flag[Q]=0/1 means that        loop-filtering is disallowed/allowed across the subpicture        boundaries of the subpicture containing Q-side.        -   a. In one example, E is not filtered if            loop_filter_across_subpic_enabled_flag[P] is equal to 0 or            loop_filter_across_subpic_enabled_flag[Q] is equal to 0.        -   b. In one example, E is not filtered if            loop_filter_across_subpic_enabled_flag[P] is equal to 0 and            loop_filter_across_subpic_enabled_flag[Q] is equal to 0.        -   c. In one example, whether to filter the two sides of E are            controlled separately.            -   i. For example, P-side of E is filtered if and only if                loop_filter_across_subpic_enabled_flag[P] is equal 1.            -   ii. For example, Q-side of E is filtered if and only if                loop_filter_across_subpic_enabled_flag[Q] is equal 1.    -   50. It is proposed that, the signaling/parsing of a syntax        element (SE) in PPS specifying the maximum block size used for        transform skip (such as log 2_transform_skip_max_size_minus2)        should be decoupled from any syntax element in SPS (such as        sps_transform_skip_enabled_flag).        -   a. An exemplary syntax change is as below:

pic_parameter_set_rbsp( ) { ...  [[if( sps_transform_skip_enabled_flag)]]   log2_transform_skip_max_size_minus2 ue(v) ...

-   -   -   b. Alternatively, SE may be signaled in SPS, such as:

seq_parameter_set_rbsp( ) { ...  if( sps_transform_skip_enabled_flag )  log2_transform_skip_max_size_minus2 ue(v) ...

-   -   -   c. Alternatively, SE may be signaled in the picture header,            such as:

picture_header_rbsp( ) { ...  if( sps_transform_skip_enabled_flag )  log2_transform_skip_max_size_minus2 ue(v) ...

-   -   51. Whether to and/or how to update the HMVP table (or named as        list/storage/map etc.) after decoding a first block may depend        on whether the first block is coded with GEO.        -   a. In one example, the HMVP table may not be updated after            decoding the first block if the first block is coded with            GEO.        -   b. In one example, the HMVP table may be updated after            decoding the first block if the first block is coded with            GEO.            -   i. In one example, the HMVP table may be updated with                the motion information of one partition divided by GEO.            -   ii. In one example, the HMVP table may be updated with                the motion information of multiple partitions divided by                GEO    -   52. In CC-ALF, luma samples out of the current processing unit        (e.g., ALF processing unit bounded by two ALF virtual        boundaries) is excluded from filtering on chroma samples in the        corresponding processing unit.        -   a. Padded luma samples out of the current processing unit            may be used to filter the chroma samples in the            corresponding processing unit.            -   i. Any padding method disclosed in this document may be                used to pad the luma samples.        -   b. Alternatively, luma samples out of the current processing            unit may be used to filter chroma samples in the            corresponding processing unit.

5. Embodiments

In the following embodiments, the newly added texts are bold italicizedand the deleted texts are marked by “[[ ]]”.

5.1 Embodiment 1: Sub-Picture Constraint on Affine Constructed MergeCandidates 8.5.5.6 Derivation Process for Constructed Affine ControlPoint Motion Vector Merging Candidates

Inputs to this process are:

-   -   a luma location (xCb, yCb) specifying the top-left sample of the        current luma coding block relative to the top-left luma sample        of the current picture,    -   two variables cbWidth and cbHeight specifying the width and the        height of the current luma coding block,    -   the availability flags availableA₀, availableA₁, availableA₂,        availableB₀, availableB₁, availableB₂, availableB₃,    -   the sample locations (xNbA₀, yNbA₀), (xNbA₁, yNbA₁), (xNbA₂,        yNbA₂), (xNbB₀, yNbB₀), (xNbB₁, yNbB₁), (xNbB₂, yNbB₂) and        (xNbB₃, yNbB₃).        Output of this process are:    -   the availability flag of the constructed affine control point        motion vector merging candidates availableFlagConstK, with K=1 .        . . 6,    -   the reference indices refIdxLXConstK, with K=1.6, X being 0 or        1,    -   the prediction list utilization flags predFlagLXConstK, with K=1        . . . 6, X being 0 or 1,    -   the affine motion model indices motionModelIdcConstK, with K=1 .        . . 6,    -   the bi-prediction weight indices bcwIdxConstK, with K=1 . . . 6,    -   the constructed affine control point motion vectors        cpMvLXConstK[cpIdx] with cpIdx=0 . . . 2, K=1 . . . 6 and X        being 0 or 1.    -   . . .        The fourth (collocated bottom-right) control point motion vector        cpMvLXCorner[3], reference index refIdxLXCorner[3], prediction        list utilization flag predFlagLXCorner[3] and the availability        flag availableFlagCorner[3] with X being 0 and 1 are derived as        follows:    -   The reference indices for the temporal merging candidate,        refIdxLXCorner[3], with X being 0 or 1, are set equal to 0.    -   The variables mvLXCol and availableFlagLXCol, with X being 0 or        1, are derived as follows:        -   If slice_temporal_mvp_enabled_flag is equal to 0, both            components of mvLXCol are set equal to 0 and            availableFlagLXCol is set equal to 0.        -   Otherwise (slice_temporal_mvp_enabled_flag is equal to 1),            the following applies:

xColBr=xCb+cbWidth  (8-601)

yColBr=yCb+cbHeight  (8-602)

-   -   -   

        -   

        -   If yCb>>CtbLog2SizeY is equal to yColBr>>CtbLog2Size Y            -   The variable colCb specifies the luma coding block                covering the modified location given by ((xColBr>>3)<<3,                (yColBr>>3)<<3) inside the collocated picture specified                by ColPic.            -   The luma location (xColCb, yColCb) is set equal to the                top-left sample of the collocated luma coding block                specified by colCb relative to the top-left luma sample                of the collocated picture specified by ColPic.            -   The derivation process for collocated motion vectors as                specified in clause 8.5.2.12 is invoked with currCb,                colCb, (xColCb, yColCb), refIdxLXCorner[3] and sbFlag                set equal to 0 as inputs, and the output is assigned to                mvLXCol and availableFlagLXCol.

        -   Otherwise, both components of mvLXCol are set equal to 0 and            availableFlagLXCol is set equal to 0.

    -   . . .

5.2 Embodiment 2: Sub-Picture Constraint on Affine Constructed MergeCandidates 8.5.5.6 Derivation Process for Constructed Affine ControlPoint Motion Vector Merging Candidates

Inputs to this process are:

-   -   a luma location (xCb, yCb) specifying the top-left sample of the        current luma coding block relative to the top-left luma sample        of the current picture,    -   two variables cbWidth and cbHeight specifying the width and the        height of the current luma coding block,    -   the availability flags availableA₀, availableA₁, availableA₂,        availableB₀, availableB₁, availableB₂, availableB₃,    -   the sample locations (xNbA₀, yNbA₀), (xNbA₁, yNbA₁), (xNbA₂,        yNbA₂), (xNbB₀, yNbB₀), (xNbB₁, yNbB₁), (xNbB₂, yNbB₂) and        (xNbB₃, yNbB₃).        Output of this process are:    -   the availability flag of the constructed affine control point        motion vector merging candidates availableFlagConstK, with K=1 .        . . 6,    -   the reference indices refIdxLXConstK, with K=1.6, X being 0 or        1,    -   the prediction list utilization flags predFlagLXConstK, with K=1        . . . 6, X being 0 or 1,    -   the affine motion model indices motionModelIdcConstK, with K=1 .        . . 6,    -   the bi-prediction weight indices bcwIdxConstK, with K=1 . . . 6,    -   the constructed affine control point motion vectors        cpMvLXConstK[cpIdx] with cpIdx=0 . . . 2, K=1 . . . 6 and X        being 0 or 1.    -   . . .        The fourth (collocated bottom-right) control point motion vector        cpMvLXCorner[3], reference index refIdxLXCorner[3], prediction        list utilization flag predFlagLXCorner[3] and the availability        flag availableFlagCorner[3] with X being 0 and 1 are derived as        follows:    -   The reference indices for the temporal merging candidate,        refIdxLXCorner[3], with X being 0 or 1, are set equal to 0.    -   The variables mvLXCol and availableFlagLXCol, with X being 0 or        1, are derived as follows:        -   If slice_temporal_mvp_enabled_flag is equal to 0, both            components of mvLXCol are set equal to 0 and            availableFlagLXCol is set equal to 0.        -   Otherwise (slice_temporal_mvp_enabled_flag is equal to 1),            the following applies:

xColBr=xCb+cbWidth  (8-601)

yColBr=yCb+cbHeight  (8-602)

rightBoundaryPos=subpic_treated_as_pic_flag[SubPicIdx]?SubPicRightBoundaryPos:pic_width_in_luma_samples−1

-   -   -   

        -   

        -   

        -   If yCb>>CtbLog2SizeY is equal to yColBr>>CtbLog2SizeY,            [[yColBr is less than pic_height_in_luma_samples and xColBr            is less than pic_width_in_luma_samples, the following            applies]]:            -   The variable colCb specifies the luma coding block                covering the modified location given by ((xColBr>>3)<<3,                (yColBr>>3)<<3) inside the collocated picture specified                by ColPic.            -   The luma location (xColCb, yColCb) is set equal to the                top-left sample of the collocated luma coding block                specified by colCb relative to the top-left luma sample                of the collocated picture specified by ColPic.            -   The derivation process for collocated motion vectors as                specified in clause 8.5.2.12 is invoked with currCb,                colCb, (xColCb, yColCb), refIdxLXCorner[3] and sbFlag                set equal to 0 as inputs, and the output is assigned to                mvLXCol and availableFlagLXCol.

        -   Otherwise, both components of mvLXCol are set equal to 0 and            availableFlagLXCol is set equal to 0.

    -   . . .

5.3 Embodiment 3: Fetching Integer Samples Under the Sub-PictureConstraint 8.5.6.3.3 Luma Integer Sample Fetching Process

Inputs to this process are:

-   -   a luma location in full-sample units (xInt_(L), yInt_(L)),

    -   the luma reference sample array refPicLX_(L),        Output of this process is a predicted luma sample value        predSampleLX_(L)        The variable shift is set equal to Max(2, 14−BitDepth_(Y)).        The variable picW is set equal to pic_width_in_luma_samples and        the variable picH is set equal to pic_height_in_luma_samples.        The luma locations in full-sample units (xInt, yInt) are derived        as follows:

    -   -   

        -   

    -   

xInt=Clip3(0,picW−1,sps_ref_wraparound_enabled_flag?ClipH((sps_ref_wraparound_offset_minus1+1)*MinCbSizeY,picW,xInt_(L)):xInt_(L))  (8-782)

yInt=Clip3(0,picH−1,yInt_(L))  (8-783)

The predicted luma sample value predSampleLX_(L) is derived as follows:

predSampleLX_(L)=refPicLX_(L) [xInt][yInt]<<shift3  (8-784)

5.4 Embodiment 4: Deriving the Variable invAvgLuma in Chroma ResidualScaling of LMCS

8.7.5.3 Picture Reconstruction with Luma Dependent Chroma ResidualScaling Process for Chroma SamplesInputs to this process are:

-   -   a chroma location (xCurr, yCurr) of the top-left chroma sample        of the current chroma transform block relative to the top-left        chroma sample of the current picture,    -   a variable nCurrSw specifying the chroma transform block width,    -   a variable nCurrSh specifying the chroma transform block height,    -   a variable tuCbfChroma specifying the coded block flag of the        current chroma transform block,    -   an (nCurrSw)×(nCurrSh) array predSamples specifying the chroma        prediction samples of the current block,    -   an (nCurrSw)×(nCurrSh) array resSamples specifying the chroma        residual samples of the current block,        Output of this process is a reconstructed chroma picture sample        array recSamples.        The variable sizeY is set equal to Min(CtbSizeY, 64).        The reconstructed chroma picture sample recSamples is derived as        follows for i=0 . . . nCurrSw−1,        j=0 . . . nCurrSh−1:    -   . . .    -   Otherwise, the following applies:        -   . . .        -   The variable currPic specifies the array of reconstructed            luma samples in the current picture.        -   For the derivation of the variable varScale the following            ordered steps apply:        -   1. The variable invAvgLuma is derived as follows:            -   The array recLuma[i] with i=0 . . . (2*sizeY−1) and the                variable cnt are derived as follows:                -   The variable cnt is set equal to 0

                -   

                -   

                -   

                -   When availL is equal to TRUE, the array recLuma[i]                    with i=0 . . . sizeY−1 is set equal to                    currPic[xCuCb−1][Min(yCuCb+i,                    [[pic_height_in_luma_samples−1]]                    )] with i=0 . . . sizeY−1, and cnt is set equal to                    sizeY

                -   When availT is equal to TRUE, the array                    recLuma[cnt+i] with i=0 . . . sizeY−1 is set equal                    to currPic[Min(xCuCb+i,                    [[pic_width_in_luma_samples−1]]                    )][yCuCb−1] with i=0 . . . sizeY−1, and cnt is set                    equal to (cnt+sizeY)            -   The variable invAvgLuma is derived as follows:                -   If cnt is greater than 0, the following applies:

invAvgLuma=Clip1_(Y)((Σ_(k=0) ^(cnt-1)recLuma[k]+(cnt>>1))>>Log2(cnt))  (8-1013)

-   -   -   -   -   Otherwise (cnt is equal to 0), the following                    applies:

invAvgLuma=1<<(BitDepth_(Y)−1)  (8-1014)

5.5 Embodiment 5: An Example of Defining the Sub-Picture Element in Unitof N (Such as N=8 or 32) Other than 4 Samples 7.4.3.3 Sequence ParameterSet RBSP Semantics

subpic_grid_col_width_minus1 plus 1 specifies the width of each elementof the sub-picture identifier grid in units of

samples. The length of the syntax element is Ceil(Log2(pic_width_max_in_luma_samples/

)) bits.The variable NumSubPicGridCols is derived as follows:

NumSubPicGridCols=(pic_width_max_in_luma_samples+subpic_grid_col_width_minus1*[[4+3]]

)/(subpic_grid_col_width_minus1*[[4+3]]

)  (7-5)

subpic_grid_row_height_minus1 plus 1 specifies the height of eachelement of the sub-picture identifier grid in units of 4 samples. Thelength of the syntax element is Ceil(Log2(pic_height_max_in_luma_samples/

) bits. The variable NumSubPicGridRows is derived as follows:

NumSubPicGridRows=(pic_height_max_in_luma_samples+subpic_grid_row_height_minus1*

)/(subpic_grid_row_height_minus1*[[4+3]]

)

7.4.7.1 General Slice Header Semantics

The variables SubPicIdx, SubPicLeftBoundaryPos, SubPicTopBoundaryPos,SubPicRightBoundaryPos, and SubPicBotBoundaryPos are derived as follows:

SubPicIdx = CtbToSubPicIdx[ CtbAddrBsToRs[ FirstCtbAddrBs[SliceBrickIdx[ 0 ] ] ] ] if( subpic_treated_as_pic_flag[ SubPicIdx ] ) { SubPicLeftBoundaryPos = SubPicLeft[ SubPicIdx ] * (subpic_grid_col_width_minus1 + 1 ) * 

 SubPicRightBoundaryPos = ( SubPicLeft[ SubPicIdx ] + SubPic Width[SubPicIdx ] ) *   ( subpic_grid_col_width_minus1 + 1 ) * 

(7-93)  SubPicTopBoundaryPos = SubPicTop[ SubPicIdx ] * (subpic_grid_row_height_minus1 + 1 )* 

 SubPicBotBoundaryPos = ( SubPicTop[ SubPicIdx ] + SubPicHeight[SubPicIdx ] ) *   ( subpic_grid_row_height_minus1 + 1 ) * 

}

5.6 Embodiment 6: Restrict the Picture Width and the Picture Height tobe Equal or Larger than 8 7.4.3.3 Sequence Parameter Set RBSP Semantics

pic_width_max_in_luma_samples specifies the maximum width, in units ofluma samples, of each decoded picture referring to the SPS.pic_width_max_in_luma_samples shall not be equal to 0 and shall be aninteger multiple of [[MinCbSizeY]]

.pic_height_max_in_luma_samples specifies the maximum height, in units ofluma samples, of each decoded picture referring to the SPS.pic_height_max_in_luma_samples shall not be equal to 0 and shall be aninteger multiple of [[MinCbSizeY]]

.

5.7 Embodiment 7: Sub-Picture Boundary Check for BT/TT/QT Splitting,BT/TT/QT Depth Derivation, and/or the Signaling of CU Split Flag 6.4.2Allowed Binary Split Process

The variable allowBtSplit is derived as follows:

-   -   . . .    -   Otherwise, if all of the following conditions are true,        allowBtSplit is set equal to FALSE        -   btSplit is equal to SPLIT_BT_VER        -   y0+cbHeight is greater than [[pic_height_in_luma_samples]]            8    -   Otherwise, if all of the following conditions are true,        allowBtSplit is set equal to FALSE        -   btSplit is equal to SPLIT_BT_VER        -   cbHeight is greater than MaxTbSizeY        -   x0+cbWidth is greater than [[pic_width_in_luma_samples]]    -   Otherwise, if all of the following conditions are true,        allowBtSplit is set equal to FALSE        -   btSplit is equal to SPLIT_BT_HOR        -   cbWidth is greater than MaxTbSizeY        -   y0+cbHeight is greater than [[pic_height_in_luma_samples]]    -   Otherwise, if all of the following conditions are true,        allowBtSplit is set equal to FALSE        -   x0+cbWidth is greater than [[pic_width_in_luma_samples]]        -   y0+cbHeight is greater than [[pic_height_in_luma_samples]]        -   cbWidth is greater than minQtSize    -   Otherwise, if all of the following conditions are true,        allowBtSplit is set equal to FALSE        -   btSplit is equal to SPLIT_BT_HOR        -   x0+cbWidth is greater than [[pic_width_in_luma_samples]]        -   y0+cbHeight is less than or equal to            [[pic_height_in_luma_samples]]

6.4.2 Allowed Ternary Split Process

The variable allowTtSplit is derived as follows:

-   -   If one or more of the following conditions are true,        allowTtSplit is set equal to FALSE:        -   cbSize is less than or equal to 2*MinTtSizeY        -   cbWidth is greater than Min(MaxTbSizeY, maxTtSize)        -   cbHeight is greater than Min(MaxTbSizeY, maxTtSize)        -   mttDepth is greater than or equal to maxMttDepth        -   x0+cbWidth is greater than [[pic_width_in_luma_samples]]        -   y0+cbHeight is greater than [[pic_height_in_luma_samples]]        -   treeType is equal to DUAL_TREE_CHROMA and            (cbWidth/SubWidthC)*(cbHeight/SubHeightC) is less than or            equal to 32        -   treeType is equal to DUAL_TREE_CHROMA and modeType is equal            to MODE_TYPE_INTRA    -   Otherwise, allowTtSplit is set equal to TRUE.

7.3.8.2 Coding Tree Unit Syntax

Descriptor dual_tree_implicit_qt_split( x0, y0, cbSize, cqtDepth ) { ...  if( x1 < [[pic_width_in_luma_samples]]] 

 

 

 

 

   dual_tree_implicit_qt_split( x1, y0, cbSize / 2, cqtDepth + 1 )   if(y1 < [[pic_height_in_luma_samples]] 

 

 

 

  

   dual_tree_implicit_qt_split( x0, y1, cbSize / 2, cqtDepth + 1)   if(x1 < [[pic_width_in_luma_samples]] 

 

 

 

 

 && y1 < [[pic_height_in_luma_samples]] 

 

 

 

 

   dual_tree_implicit_qt_split( x1, y1, cbSize / 2, cqtDepth + 1 )  }else { ...  }

7.3.8.4 Coding Tree Syntax

Descriptor coding_tree( x0, y0, cbWidth, cbHeight, qgOnY, qgOnC,cbSubdiv, cqtDepth, mttDepth, depthOffset,       partIdx, treeTypeCurr,modeTypeCurr ) {  if( ( allowSpltBtVer ∥ allowSplitBtHor ∥allowSplitTtVer ∥ allowSplitTtHor ∥ allowSplitQT )    &&( x0 + cbWidth<= [[pic_width_in_luma_samples]]

 

 

   && (y0 + cbHeight <= [[pic_height_in_luma_samples]]

 

 

 

  split_cu_flag ae(v)  if( cu_qp_delta_enabled_flag && qgOnY && cbSubdiv<= cu_qp_delta_subdiv ) { ...     depthOffset += ( y0 + cbHeight >[[pic_height_in_luma_samples]]

 

 

 ) ) ? 1 : 0     y1 = y0 + ( cbHeight / 2 )     coding_tree( x0, y0,cbWidth, cbHeight / 2, qgOnY, qgOnC, cbSubdiv + 1,         cqtDepth,mttDepth + 1, depthOffset, 0, treeType, modeType )    if( y1 <[[pic_height_in_luma_samples]] 

 

 

 

     coding_tree( x0, y1, cbWidth, cbHeight / 2, qgOnY, qgOnC,cbSubdiv + 1,          cqtDepth, mttDepth + 1, depthOffset, 1, treeType,modeType ) ...    if( x1 < [[pic_width_in_luma_samples]] 

 

 

 

 

    coding_tree( x1, y0, cbWidth / 2, cbHeight / 2, qgOnY, qgOnC,cbSubdiv + 2,        cqtDepth + 1, 0, 0, 1, treeType, modeType )    if(y1 < [[pic_height_in_luma_samples]] 

 

 

 

 

    coding_tree( x0, y1, cbWidth / 2, cbHeight / 2, qgOnY, qgOnC,cbSubdiv + 2,        cqtDepth + 1, 0, 0, 0, treeType, modeType )    if(y1 < [[pic_height_in_luma_samples]] 

 

 

 

 

[[pic_width_in_luma_samples]] 

 

 

 

    coding_tree( x1, y1, cbWidth / 2, cbHeight / 2, qgOnY, qgOnC,cbSubfiv + 2,        cqtDepth + 1, 0, 0, 3, treeType, modeType )

5.8 Embodiment 8: An Example of Defining the Sub-Pictures

Descriptor seq_parameter_set_rbsp( ) {  sps_decoding_parameter_set_idu(4) ...  pic_width_max_in_luma_samples ue(v) pic_height_max_in_luma_samples ue(v)   [ [subpics_present_flag u(1) if( subpics_present_flag ) {   max_subpics_minus1 u(8)  subpic_grid_col_width_minus1 u(v)   subpic_grid_row_height_minus1 u(v)  for( i = 0; i < NumSubPicGridRows; i++ )    for( j = 0; j <NumSubPicGridCols; j++ )     subpic_grid_idx[ i ][ j ] u(v)   for( i =0; i <= NumSubPics; i++ ) {    subpic_treated_as_pic_flag[ i ] u(1)   loop_filter_across_subpic_enabled_flag[ i ] u(1)   }  }]] bit_depth_luma_minus8 ue(v)   ...  log2_ctu_size_minus5 u(2) ...  

 

  

  

 

   

   

   

   

   

   

 

  } ...

5.9 Embodiment 9: An Example of Defining the Sub-Pictures

Descriptor seq_parameter_set_rbsp( ) {  sps_decoding_parameter_set_idu(4) ...  pic_width_max_in_luma_samples ue(v) pic_height_max_in_luma_samples ue(v)   [ [ subpics_present_flag u(1) if( subpics_present_flag ) {   max_subpics_minus1 u(8)  subpic_grid_col_width_minus1 u(v)   subpic_grid_row_height_minus1 u(v)  for( i = 0; i < NumSubPicGridRows; i++ )    for( j = 0; j <NumSubPicGridCols; j++ )     subpic_grid_idx[ i ][ j ] u(v)   for( i =0; i <= NumSubPics; i++ ) {    subpic_treated_as_pic_flag[ i ] u(1)   loop_filter_across_subpic_enabled_flag[ i ] u(1)   }  }]] bit_depth_luma_minus8 ue(v) ...  log2_ctu_size_minus5 u(2) ...  

 

  

  

 

   

   

   

   

   

 

   

 

  } ...

5.10 Embodiment 10: An Example of Defining the Sub-Pictures

Descriptor seq_parameter_set_rbsp( ) {  sps_decoding_parameter_set_idu(4) ...  pic_width_max_in_luma_samples ue(v) pic_height_max_in_luma_samples ue(v)   [ [ subpics_present_flag u(1) if( subpics_present_flag ) {    max_subpics_minus1 u(8)   subpic_grid_col_width_minus1 u(v)    subpic_grid_row_height_minus1u(v)    for( i = 0; i < NumSubPicGridRows; i++ )     for( j = 0; j <NumSubPicGridCols; j++ )      subpic_grid_idx[ i ][ j ] u(v)    for( i =0; i <= NumSubPics; i++ ) {     subpic_treated_as_pic_flag[ i ] u(1)    loop_filter_across_subpic_enabled_flag[ i ] u(1)    }  }]] ... log2_ctu_size_minus5 u(2) ...  

 

   

  subpic_addr_x_length_minus1

  subpic_addr_y_length_minus1

   

    

    

    

    

    

    

 

  } ...

5.11 Embodiment 11: An Example of Defining the Sub-Pictures

Descriptor seq_parameter_set_rbsp( ) {  sps_decoding_parameter_set_idu(4) ...  pic_width_max_in_luma_samples ue(v) pic_height_max_in_luma_samples ue(v)   [ [subpics_present_flag u(1) if( subpics_present_flag ) {    max_subpics_minus1 u(8)   subpic_grid_col_width_minus1 u(v)    subpic_grid_row_height_minus1u(v)    for( i = 0; i < NumSubPicGridRows; i++ )      for( j = 0; j <NumSubPicGridCols; j++)       subpic_grid_idx[ i ][ j ] u(v)    for( i =0; i <= NumSubPics; i++ ) {      subpic_treated_as_pic_flag[ i ] u(1)     loop_filter_across_subpic_enabled_flag[ i ] u(1)    }  }]] ... log2_ctu_size_minus5 u(2) ...  

 

   

  subpic_addr_x_length_minus1

  subpic_addr_y_length_minus1

   

 

    

     

     

     

 

     

 

    

     

 

     

 

  } ...

NumSubPics=num_subpics_minus2+2. 5.12 Embodiment: Deblocking ConsideringSub-Pictures Deblocking Filter Process General

Inputs to this process are the reconstructed picture prior todeblocking, i.e., the array recPicture_(L) and, when ChromaArrayType isnot equal to 0, the arrays recPicture_(Cb) and recPicture_(Cr).Outputs of this process are the modified reconstructed picture afterdeblocking, i.e., the array recPicture_(L) and, when ChromaArrayType isnot equal to 0, the arrays recPicture_(Cb) and recPicture_(Cr).The vertical edges in a picture are filtered first. Then the horizontaledges in a picture are filtered with samples modified by the verticaledge filtering process as input. The vertical and horizontal edges inthe CTBs of each CTU are processed separately on a coding unit basis.The vertical edges of the coding blocks in a coding unit are filteredstarting with the edge on the left-hand side of the coding blocksproceeding through the edges towards the right-hand side of the codingblocks in their geometrical order. The horizontal edges of the codingblocks in a coding unit are filtered starting with the edge on the topof the coding blocks proceeding through the edges towards the bottom ofthe coding blocks in their geometrical order.

-   -   NOTE—Although the filtering process is specified on a picture        basis in this Specification, the filtering process can be        implemented on a coding unit basis with an equivalent result,        provided the decoder properly accounts for the processing        dependency order so as to produce the same output values.        The deblocking filter process is applied to all coding subblock        edges and transform block edges of a picture, except the        following types of edges:    -   Edges that are at the boundary of the picture,    -   [[Edges that coincide with the boundaries of a subpicture for        which loop_filter_across_subpic_enabled_flag[SubPicIdx] is equal        to 0,]]    -   Edges that coincide with the virtual boundaries of the picture        when pps_loop_filter_across_virtual_boundaries_disabled_flag is        equal to 1,    -   Edges that coincide with tile boundaries when        loop_filter_across_tiles_enabled_flag is equal to 0,    -   Edges that coincide with slice boundaries when        loop_filter_across_slices_enabled_flag is equal to 0,    -   Edges that coincide with upper or left boundaries of slices with        slice_deblocking_filter_disabled_flag equal to 1,    -   Edges within slices with slice_deblocking_filter_disabled_flag        equal to 1,    -   Edges that do not correspond to 4×4 sample grid boundaries of        the luma component,    -   Edges that do not correspond to 8×8 sample grid boundaries of        the chroma component,    -   Edges within the luma component for which both sides of the edge        have intra_bdpcm_luma_flag equal to 1,    -   Edges within the chroma components for which both sides of the        edge have intra_bdpcm_chroma_flag equal to 1,    -   Edges of chroma subblocks that are not edges of the associated        transform unit.

Deblocking Filter Process for One Direction

Inputs to this process are:

-   -   the variable treeType specifying whether the luma        (DUAL_TREE_LUMA) or chroma components (DUAL_TREE_CHROMA) are        currently processed,    -   when treeType is equal to DUAL_TREE_LUMA, the reconstructed        picture prior to deblocking, i.e., the array recPicture_(L),    -   when ChromaArrayType is not equal to 0 and treeType is equal to        DUAL_TREE_CHROMA, the arrays recPicture_(Cb) and        recPicture_(Cr),    -   a variable edgeType specifying whether a vertical (EDGE_VER) or        a horizontal (EDGE_HOR) edge is filtered.        Outputs of this process are the modified reconstructed picture        after deblocking, i.e:    -   when treeType is equal to DUAL_TREE_LUMA, the array        recPicture_(L),    -   when ChromaArrayType is not equal to 0 and treeType is equal to        DUAL_TREE_CHROMA, the arrays recPicture_(Cb) and        recPicture_(Cr).        The variables firstCompIdx and lastCompIdx are derived as        follows:

firstCompIdx=(treeType==DUAL_TREE_CHROMA)?1:0  (8-1010)

lastCompIdx=(treeType==DUAL_TREE_LUMA ChromaArrayType==0)?0:2  (8-1011)

For each coding unit and each coding block per colour component of acoding unit indicated by the colour component index cIdx ranging fromfirstCompIdx to lastCompIdx, inclusive, with coding block width nCbW,coding block height nCbH and location of top-left sample of the codingblock (xCb, yCb), when cIdx is equal to 0, or when cIdx is not equal to0 and edgeType is equal to EDGE_VER and xCb % 8 is equal 0, or when cIdxis not equal to 0 and edgeType is equal to EDGE_HOR and yCb % 8 is equalto 0, the edges are filtered by the following ordered steps:

-   -   2. The variable filterEdgeFlag is derived as follows:        -   If edgeType is equal to EDGE_VER and one or more of the            following conditions are true, filterEdgeFlag is set equal            to 0:            -   The left boundary of the current coding block is the                left boundary of the picture.            -   [[The left boundary of the current coding block is the                left or right boundary of the subpicture and                loop_filter_across_subpic_enabled_flag[SubPicIdx] is                equal to 0.]]            -   The left boundary of the current coding block is the                left boundary of the tile and                loop_filter_across_tiles_enabled_flag is equal to 0.            -   The left boundary of the current coding block is the                left boundary of the slice and                loop_filter_across_slices_enabled_flag is equal to 0.            -   The left boundary of the current coding block is one of                the vertical virtual boundaries of the picture and                VirtualBoundariesDisabledFlag is equal to 1.        -   Otherwise, if edgeType is equal to EDGE_HOR and one or more            of the following conditions are true, the variable            filterEdgeFlag is set equal to 0:            -   The top boundary of the current luma coding block is the                top boundary of the picture.            -   [[The top boundary of the current coding block is the                top or bottom boundary of the subpicture and                loop_filter_across_subpic_enabled_flag[SubPicIdx] is                equal to 0.]]            -   The top boundary of the current coding block is the top                boundary of the tile and                loop_filter_across_tiles_enabled_flag is equal to 0.            -   The top boundary of the current coding block is the top                boundary of the slice and                loop_filter_across_slices_enabled_flag is equal to 0.            -   The top boundary of the current coding block is one of                the horizontal virtual boundaries of the picture and                VirtualBoundariesDisabledFlag is equal to 1.        -   Otherwise, filterEdgeFlag is set equal to 1.            . . .

Filtering Process for a Luma Sample Using Short Filters

Inputs to this process are:

-   -   the sample values p_(i) and q_(i) with i=0 . . . 3,    -   the locations of p_(i) and q_(i), (xP_(i), yP_(i)) and (xQ_(i),        yQ_(i)) with i=0 . . . 2,    -   a variable dE,    -   the variables dEp and dEq containing decisions to filter samples        p1 and q1, respectively,    -   a variable t_(C).        Outputs of this process are:    -   the number of filtered samples nDp and nDq,    -   the filtered sample values p_(i)′ and g_(j)′ with i=0 . . .        nDp−1, j=0 . . . nDq−1.        Depending on the value of dE, the following applies:    -   If the variable dE is equal to 2, nDp and nDq are both set equal        to 3 and the following strong filtering applies:

p ₀′=Clip3(p ₀−3*t _(C) ,p ₀+3*t _(C),(p ₂+2*p ₁+2*p ₀+² *q ₀ +q₁+4)>>3)  (8-1150)

p ₁′=Clip3(p ₁−2*t _(C) ,p ₁+2*t _(C),(p ₂ +p ₁ +p ₀ +q₀+2)>>2)  (8-1151)

p ₂′=Clip3(p ₂−1*t _(C) ,p ₂+1*t _(C),(2*p ₃+3*p ₂ +p ₁ +p ₀ +q₀+4)>>3)  (8-1152)

q ₀′=Clip3(q ₀−3*t _(C) ,q ₀+3*t _(C),(p ₁+2*p ₀+2*q ₀+2*q ₁ +q₂+4)>>3)  (8-1153)

q ₁′=Clip3(q ₁−2*t _(C) ,q ₁+2*t _(C),(p ₀ +q ₀ +q ₁ +q₂+2)>>2)  (8-1154)

q ₂′=Clip3(q ₂−1*t _(C) ,q ₂+1*t _(C),(p ₀ +q ₀ +q ₁+3*q ₂+2*q₃+4)>>3)  (8-1155)

-   -   Otherwise, nDp and nDq are set both equal to 0 and the following        weak filtering applies:        -   The following applies:

Δ=(9*(q ₀ −p ₀)−3*(q ₁ −p ₁)+8)>>4  (8-1156)

-   -   -   When Abs(Δ) is less than t_(C)*10, the following ordered            steps apply:            -   The filtered sample values p₀′ and q₀′ are specified as                follows:

Δ=Clip3(−t _(C) ,t _(C),Δ)  (8-1157)

p ₀′=Clip1(p ₀+Δ)  (8-1158)

q ₀′=Clip1(q ₀−Δ)  (8-1159)

-   -   -   -   When dEp is equal to 1, the filtered sample value p₁′ is                specified as follows:

Δp=Clip3(−(t _(C)>>1),t _(C)>>1,(((p ₂ +p ₀+1)>>1)p ₁+Δ)>>1)  (8-1160)

p ₁′=Clip1(p ₁ +Δp)  (8-1161)

-   -   -   -   When dEq is equal to 1, the filtered sample value q₁′ is                specified as follows:

Δq=Clip3(−(t _(C)>>1),t _(C)>>1,(((q ₂ +q ₀+1)>>1)−q ₁−Δ)>>1)  (8-1162)

q ₁′=Clip1(q ₁ +Δq)  (8-1163)

-   -   -   -   nDp is set equal to dEp+1 and nDq is set equal to dEq+1.                When nDp is greater than 0 and pred_mode_plt_flag of the                coding unit that includes the coding block containing                the sample p₀ is equal to 1, nDp is set equal to 0                When nDq is greater than 0 and pred_mode_plt_flag of the                coding unit that includes the coding block containing                the sample q₀ is equal to 1 nDq is set equal to 0

Filtering Process for a Luma Sample Using Long Filters

Inputs to this process are:

-   -   the variables maxFilterLengthP and maxFilterLengthQ,    -   the sample values p_(i) and q_(i) with i=0 . . .        maxFilterLengthP and j=0 . . . maxFilterLengthQ,    -   the locations of p_(i) and q_(j), (xP_(i), yP_(i)) and (xQ_(j),        yQ_(j)) with i=0 . . . maxFilterLengthP−1 and j=0 . . .        maxFilterLengthQ−1,    -   a variable t_(C).        Outputs of this process are:    -   the filtered sample values p_(i)′ and q_(j)′ with i=0 . . .        maxFilterLengthP−1, j=0 . . . maxFilterLenghtQ−1.        The variable refMiddle is derived as follows:    -   If maxFilterLengthP is equal to maxFilterLengthQ and        maxFilterLengthP is equal to 5, the following applies:

refMiddle=(p ₄ +p ₃+2*(p ₂ +p ₁ +p ₀ +q ₀ +q ₁ +q ₂)+q ₃ +q₄+8)>>4  (8-1164)

-   -   Otherwise, if maxFilterLengthP is equal to maxFilterLengthQ and        maxFilterLengthP is not equal to 5, the following applies:

refMiddle=(p ₆ +p ₅ +p ₄ +p ₃ +p ₂ +p ₁+2*(p ₀ +q ₀)+q ₁ +q ₂ +q ₃ +q ₄+q ₅ +q ₆+8)>>4  (8-1165)

-   -   Otherwise, if one of the following conditions are true,        -   maxFilterLengthQ is equal to 7 and maxFilterLengthP is equal            to 5,        -   maxFilterLengthQ is equal to 5 and maxFilterLengthP is equal            to 7,    -   the following applies:

refMiddle=(p ₅ +p ₄ +p ₃ +p ₂+2*(p ₁ +p ₀ +q ₀ +q ₁)+q ₂ +q ₃ +q ₄ +q₅+8)>>4  (8-1166)

-   -   Otherwise, if one of the following conditions are true,        -   maxFilterLengthQ is equal to 5 and maxFilterLengthP is equal            to 3,        -   maxFilterLengthQ is equal to 3 and maxFilterLengthP is equal            to 5,    -   the following applies:

refMiddle=(p ₃ +p ₂ +p ₁ +p ₀ +q ₀ +q ₁ +q ₂ +q ₃+4)>>3  (8-1167)

-   -   Otherwise, if maxFilterLengthQ is equal to 7 and        maxFilterLengthP is equal to 3, the following applies:

refMiddle=(2*(p ₂ +p ₁ +p ₀ +q ₀)+p ₀ +p ₁ +q ₁ +q ₂ +q ₃ +q ₄ +q ₅ +q₆+8)>>4  (8-1168)

-   -   Otherwise, the following applies:

refMiddle=(p ₆ +p ₅ +p ₄ +p ₃ +p ₂ +p ₁+2*(q ₂ +q ₁ +q ₀ +p ₀)+q ₀ +q₁+8)>>4  (8-1169)

The variables refP and refQ are derived as follows:

refP=(p _(maxFilterLengtP) +p _(maxFilterLengthP-1)+1)>>1  (8-1179)

refQ=(q _(maxFilterLengtQ) +q _(maxFilterLengthQ-1)+1)>>1  (8-1171)

The variables f_(i) and t_(C)PD_(i) are defined as follows:

-   -   If maxFilterLengthP is equal to 7, the following applies:

f _(0 . . . 6)={59,50,41,32,23,14,5}  (8-1172)

t _(C) PD _(0 . . . 6)={6,5,4,3,2,1,1}  (8-1173)

-   -   Otherwise, if maxFilterLengthP is equal to 5, the following        applies:

f _(0 . . . 4)={58,45,32,19,6}  (8-1174)

t _(C) PD _(0 . . . 4)={6,5,4,3,2}  (8-1175)

-   -   Otherwise, the following applies:

f _(0 . . . 2)={53,32,11}  (8-1176)

t _(C) PD _(0 . . . 2)={6,4,2}  (8-1177)

-   -   The variables g_(j) and t_(C)QD_(j) are defined as follows:    -   If maxFilterLengthQ is equal to 7, the following applies:

q _(0 . . . 6)={59,50,41,32,23,14,5}  (8-1178)

t _(C) QD _(0 . . . 6)={6,5,4,3,2,1,1}  (8-1179)

-   -   Otherwise, if maxFilterLengthQ is equal to 5, the following        applies:

g _(0 . . . 4)={58,45,32,19,6}  (8-1180)

t _(C) QD _(0 . . . 4)={6,5,4,3,2}  (8-1181)

-   -   Otherwise, the following applies:

g _(0 . . . 2)={53,32,11}  (8-1182)

t _(C) QD _(0 . . . 2)={6,4,2}  (8-1183)

The filtered sample values p_(i)′ and g_(j)′ with i=0 . . .maxFilterLengthP−1 and j=0 . . . maxFilterLengthQ−1 are derived asfollows:

p _(i)′=Clip3(p _(i)−(t _(C) *t _(C) PD _(i))>>1,p _(i)+(t _(C) *t _(C)PD _(i))>>1,(refMiddle*f _(i)+refP*(64−f _(i))+32)>>6)  (8-1184)

q _(j)′=Clip3(q _(j)−(t _(C) *t _(C) QD _(j))>>1,q _(j)+(t _(C) *t _(C)QD _(j))>>1,(refMiddle*g _(j)+refQ*(64−g _(j))+32)>>6)  (8-1185)

When pred_mode_plt_flag of the coding unit that includes the codingblock containing the sample p_(i) is equal to 1, the filtered samplevalue, p_(i)′ is substituted by the corresponding input sample valuep_(i) with i=0 . . . maxFilterLengthP−1.When pred_mode_plt_flag of the coding unit that includes the codingblock containing the sample q_(i) is equal to 1, the filtered samplevalue, q_(i)′ is substituted by the corresponding input sample valueq_(j) with i=0 . . . maxFilterLengthQ−1.

Filtering Process for a Chroma Sample

This process is only invoked when ChromaArrayType is not equal to 0.Inputs to this process are:

-   -   the variable maxFilterLength,    -   the chroma sample values p_(i) and q_(i) with i=0 . . .        maxFilterLengthCbCr,    -   the chroma locations of p_(i) and q_(i), (xP_(i), yP_(i)) and        (xQ_(i), yQ_(i)) with i=0 . . . maxFilterLengthCbCr−1,    -   a variable t_(C).        Outputs of this process are the filtered sample values p_(i)′        and q_(i)′ with i=0 . . . maxFilterLengthCbCr−1.        The filtered sample values p_(i)′ and q_(i)′ with i=0 . . .        maxFilterLengthCbCr−1 are derived as follows:    -   If maxFilterLengthCbCr is equal to 3, the following strong        filtering applies:

p ₀′=Clip3(p ₀ −t _(C) ,p ₀ +t _(C),(p ₃ +p ₂ +p ₁+2*p ₀ +q ₀ +q ₁ +q₂+4)>>3)  (8-1186)

p ₁′=Clip3(p ₁ −t _(C) ,p ₁ +t _(C),(2*p ₃ +p ₂+2*p ₁ +p ₀ +q ₀ +q₁+4)>>3)  (8-1187)

p ₂′=Clip3(p ₂ −t _(C) ,p ₂ +t _(C),(3*p ₃+2*p ₂ +p ₁ +p ₀ +q₀+4)>>3)  (8-1188)

q ₀′=Clip3(q ₀ −t _(C) ,q ₀ +t _(C),(p ₂ +p ₁ +p ₀+2*q ₀ +q ₁ +q ₂ +q₃+4)>>3)  (8-1189)

q ₁′=Clip3(q ₁ −t _(C) ,q ₁ +t _(C),(p ₁ +p ₀ +q ₀+2*q ₁ +q ₂+2*q₃+4)>>3)  (8-1190)

q ₂′=Clip3(q ₂ −t _(C) ,q ₂ +t _(C),(p ₀ +q ₀ +q ₁+2*q ₂+3*q₃+4)>>3)  (8-1191)

-   -   Otherwise, the following weak filtering applies:

Δ=Clip3(−t _(C) ,t _(C),((((q ₀ −p ₀)<<2)+p ₁ −q ₁+4)>>3))  (8-1192)

p ₀′=Clip1(p ₀+Δ)  (8-1193)

q ₀′=Clip1(q ₀−Δ)  (8-1194)

When pred_mode_plt_flag of the coding unit that includes the codingblock containing the sample p_(i) is equal to 1, the filtered samplevalue, p_(i)′ is substituted by the corresponding input sample valuep_(i) with i=0 . . . maxFilterLengthCbCr−1.When pred_mode_plt_flag of the coding unit that includes the codingblock containing the sample q_(i) is equal to 1, the filtered samplevalue, q_(i)′ is substituted by the corresponding input sample valueq_(i) with i=0 . . . maxFilterLengthCbCr−1:

FIG. 3 is a block diagram of a video processing apparatus 300. Theapparatus 300 may be used to implement one or more of the methodsdescribed herein. The apparatus 300 may be embodied in a smartphone,tablet, computer, Internet of Things (IoT) receiver, and so on. Theapparatus 300 may include one or more processors 312, one or morememories 314 and video processing hardware 316. The processor(s) 312 maybe configured to implement one or more methods described in the presentdocument. The memory (memories) 314 may be used for storing data andcode used for implementing the methods and techniques described herein.The video processing hardware 316 may be used to implement, in hardwarecircuitry, some techniques described in the present document.

FIG. 4 is a flowchart for a method 400 of processing a video. The method400 includes determining (402), for a video block in a first videoregion of a video, whether a position at which a temporal motion vectorpredictor is determined for a conversion between the video block and abitstream representation of the current video block using an affine modeis within a second video region, and performing (404) the conversionbased on the determining.

The following solutions may be implemented as preferred solutions insome embodiments.

The following solutions may be implemented together with additionaltechniques described in items listed in the previous section (e.g., item1).

1. A method of video processing, comprising: determining, for a videoblock in a first video region of a video, whether a position at which atemporal motion vector predictor is determined for a conversion betweenthe video block and a bitstream representation of the current videoblock using an affine mode is within a second video region; andperforming the conversion based on the determining.

2. The method of solution 1, wherein the video block is covered by thefirst region and the second region.

3. The method of any of solutions 1-2, wherein, in case that theposition of the temporal motion vector predictor is outside of thesecond video region, then the temporal motion vector predictor is markedas unavailable and is unused in the conversion.

The following solutions may be implemented together with additionaltechniques described in items listed in the previous section (e.g., item2).

4. A method of video processing, comprising: determining, for a videoblock in a first video region of a video, whether a position at which aninteger sample in a reference picture is fetched for a conversionbetween the video block and a bitstream representation of the currentvideo block is within a second video region, wherein the referencepicture is not used in an interpolation process during the conversion;and performing the conversion based on the determining.

5. The method of solution 4, wherein the video block is covered by thefirst region and the second region.

6. The method of any of solutions 4-5, wherein, in case that theposition of the sample is outside of the second video region, then thesample is marked as unavailable and is unused in the conversion.

The following solutions may be implemented together with additionaltechniques described in items listed in the previous section (e.g., item3).

7. A method of video processing, comprising: determining, for a videoblock in a first video region of a video, whether a position at which areconstructed luma sample value is fetched for a conversion between thevideo block and a bitstream representation of the current video block iswithin a second video region; and performing the conversion based on thedetermining.

8. The method of solution 7, wherein the luma sample is covered by thefirst region and the second region.

9. The method of any of solutions 7-8, wherein, in case that theposition of the luma sample is outside of the second video region, thenthe luma sample is marked as unavailable and is unused in theconversion.

The following solutions may be implemented together with additionaltechniques described in items listed in the previous section (e.g., item4).

10. A method of video processing, comprising: determining, for a videoblock in a first video region of a video, whether a position at which acheck regarding splitting, depth derivation or split flag signaling forthe video block is performed during a conversion between the video blockand a bitstream representation of the current video block is within asecond video region; and performing the conversion based on thedetermining.

11. The method of solution 10, wherein the position is covered by thefirst region and the second region.

12. The method of any of solutions 10-11, wherein, in case that theposition is outside of the second video region, then the luma sample ismarked as unavailable and is unused in the conversion.

The following solutions may be implemented together with additionaltechniques described in items listed in the previous section (e.g., item8).

13. A method of video processing, comprising: performing a conversionbetween a video comprising one or more video pictures comprising one ormore video blocks, and a coded representation of the video, wherein thecoded representation complies with a coding syntax requirement that theconversion is not to use sub-picture coding/decoding and a dynamicresolution conversion coding/decoding tool or a reference pictureresampling tool within a video unit.

14. The method of solution 13, wherein the video unit corresponds to asequence of the one or more video pictures.

15. The method of any of solutions 13-14, wherein the dynamic resolutionconversion coding/decoding tool comprises an adaptive resolutionconversion coding/decoding tool.

16. The method of any of solutions 13-14, wherein the dynamic resolutionconversion coding/decoding tool comprises a dynamic resolutionconversion coding/decoding tool.

17. The method of any of solutions 13-16, wherein the codedrepresentation indicates that the video unit complies with the codingsyntax requirement.

18. The method of solution 17, wherein the coded representationindicates that the video unit uses sub-picture coding.

19. The method of solution 17, wherein the coded representationindicates that the video unit uses the dynamic resolution conversioncoding/decoding tool or the reference picture resampling tool.

The following solutions may be implemented together with additionaltechniques described in items listed in the previous section (e.g., item10).

20. The method of any of solutions 1-19, wherein the second video regioncomprises a video sub-picture and wherein boundaries of the second videoregion and another video region is also a boundary between two codingtree units.

21. The method of any of solutions 1-19, wherein the second video regioncomprises a video sub-picture and wherein boundaries of the second videoregion and another video region is also a boundary between two codingtree units.

The following solutions may be implemented together with additionaltechniques described in items listed in the previous section (e.g., item11).

22. The method of any of solutions 1-21, wherein the first video regionand the second video region have rectangular shapes.

The following solutions may be implemented together with additionaltechniques described in items listed in the previous section (e.g., item12).

23. The method of any of solutions 1-22, wherein the first video regionand the second video region are non-overlapping.

The following solutions may be implemented together with additionaltechniques described in items listed in the previous section (e.g., item13).

24. The method of any of solutions 1-23, wherein the video picture isdivided into video regions such that a pixel in the video picture iscovered by one and only one video region.

The following solutions may be implemented together with additionaltechniques described in items listed in the previous section (e.g., item15).

25. The method of any of solutions 1-24, wherein the video picture issplit into the first video region and the second video region due to thevideo picture being in a specific layer of the video sequence.

The following solutions may be implemented together with additionaltechniques described in items listed in the previous section (e.g., item10).

26. A method of video processing, comprising: performing a conversionbetween a video comprising one or more video pictures comprising one ormore video blocks, and a coded representation of the video, wherein thecoded representation complies with a coding syntax requirement that afirst syntax element subpic_grid_idx[i][j] is not larger than a secondsyntax element max_subpics_minus1.

27. The method of solution 26, wherein a codeword representing the firstsyntax element is not larger than a codeword representing the secondsyntax element.

28. The method of any of solutions 1-27, wherein the first video regioncomprises a video sub-picture.

29. The method of any of solutions 1-28, wherein the second video regioncomprises a video sub-picture.

30. The method of any of solutions 1 to 29, wherein the conversioncomprises encoding the video into the coded representation.

31. The method of any of solutions 1 to 29, wherein the conversioncomprises decoding the coded representation to generate pixel values ofthe video.

32. A video decoding apparatus comprising a processor configured toimplement a method recited in one or more of solutions 1 to 31.

33. A video encoding apparatus comprising a processor configured toimplement a method recited in one or more of solutions 1 to 31.

34. A computer program product having computer code stored thereon, thecode, when executed by a processor, causes the processor to implement amethod recited in any of solutions 1 to 31.

35. A method, apparatus or system described in the present document.

FIG. 8 is a block diagram showing an example video processing system 800in which various techniques disclosed herein may be implemented. Variousimplementations may include some or all of the components of the system800. The system 800 may include input 802 for receiving video content.The video content may be received in a raw or uncompressed format, e.g.,8 or 10 bit multi-component pixel values, or may be in a compressed orencoded format. The input 802 may represent a network interface, aperipheral bus interface, or a storage interface. Examples of networkinterface include wired interfaces such as Ethernet, passive opticalnetwork (PON), etc. and wireless interfaces such as Wi-Fi or cellularinterfaces.

The system 800 may include a coding component 804 that may implement thevarious coding or encoding methods described in the present document.The coding component 804 may reduce the average bitrate of video fromthe input 802 to the output of the coding component 804 to produce acoded representation of the video. The coding techniques are thereforesometimes called video compression or video transcoding techniques. Theoutput of the coding component 804 may be either stored, or transmittedvia a communication connected, as represented by the component 806. Thestored or communicated bitstream (or coded) representation of the videoreceived at the input 802 may be used by the component 808 forgenerating pixel values or displayable video that is sent to a displayinterface 810. The process of generating user-viewable video from thebitstream representation is sometimes called video decompression.Furthermore, while certain video processing operations are referred toas “coding” operations or tools, it will be appreciated that the codingtools or operations are used at an encoder and corresponding decodingtools or operations that reverse the results of the coding will beperformed by a decoder.

Examples of a peripheral bus interface or a display interface mayinclude universal serial bus (USB) or high definition multimediainterface (HDMI) or Displayport, and so on. Examples of storageinterfaces include serial advanced technology attachment (SATA),peripheral component interconnect (PCI), integrated drive electronics(IDE) interface, and the like. The techniques described in the presentdocument may be embodied in various electronic devices such as mobilephones, laptops, smartphones or other devices that are capable ofperforming digital data processing and/or video display.

FIG. 9 is a block diagram that illustrates an example video codingsystem 100 that may utilize the techniques of this disclosure.

As shown in FIG. 9 , video coding system 100 may include a source device110 and a destination device 120. Source device 110 generates encodedvideo data which may be referred to as a video encoding device.Destination device 120 may decode the encoded video data generated bysource device 110 which may be referred to as a video decoding device.

Source device 110 may include a video source 112, a video encoder 114,and an input/output (I/O) interface 116.

Video source 112 may include a source such as a video capture device, aninterface to receive video data from a video content provider, and/or acomputer graphics system for generating video data, or a combination ofsuch sources. The video data may comprise one or more pictures. Videoencoder 114 encodes the video data from video source 112 to generate abitstream. The bitstream may include a sequence of bits that form acoded representation of the video data. The bitstream may include codedpictures and associated data. The coded picture is a codedrepresentation of a picture. The associated data may include sequenceparameter sets, picture parameter sets, and other syntax structures. I/Ointerface 116 may include a modulator/demodulator (modem) and/or atransmitter. The encoded video data may be transmitted directly todestination device 120 via I/O interface 116 through network 130 a. Theencoded video data may also be stored onto a storage medium/server 130 bfor access by destination device 120.

Destination device 120 may include an I/O interface 126, a video decoder124, and a display device 122.

I/O interface 126 may include a receiver and/or a modem. I/O interface126 may acquire encoded video data from the source device 110 or thestorage medium/server 130 b. Video decoder 124 may decode the encodedvideo data. Display device 122 may display the decoded video data to auser. Display device 122 may be integrated with the destination device120, or may be external to destination device 120 which be configured tointerface with an external display device.

Video encoder 114 and video decoder 124 may operate according to a videocompression standard, such as the High Efficiency Video Coding (HEVC)standard, Versatile Video Coding (VVC) standard and other current and/orfurther standards.

FIG. 10 is a block diagram illustrating an example of video encoder 200,which may be video encoder 114 in the system 100 illustrated in FIG. 9 .

Video encoder 200 may be configured to perform any or all of thetechniques of this disclosure. In the example of FIG. 10 , video encoder200 includes a plurality of functional components. The techniquesdescribed in this disclosure may be shared among the various componentsof video encoder 200. In some examples, a processor may be configured toperform any or all of the techniques described in this disclosure.

The functional components of video encoder 200 may include a partitionunit 201, a prediction unit 202 which may include a mode select unit203, a motion estimation unit 204, a motion compensation unit 205 and anintra prediction unit 206, a residual generation unit 207, a transformunit 208, a quantization unit 209, an inverse quantization unit 210, aninverse transform unit 211, a reconstruction unit 212, a buffer 213, andan entropy encoding unit 214.

In other examples, video encoder 200 may include more, fewer, ordifferent functional components. In an example, prediction unit 202 mayinclude an intra block copy (IBC) unit. The IBC unit may performprediction in an IBC mode in which at least one reference picture is apicture where the current video block is located.

Furthermore, some components, such as motion estimation unit 204 andmotion compensation unit 205 may be highly integrated, but arerepresented in the example of FIG. 5 separately for purposes ofexplanation.

Partition unit 201 may partition a picture into one or more videoblocks. Video encoder 200 and video decoder 300 may support variousvideo block sizes.

Mode select unit 203 may select one of the coding modes, intra or inter,e.g., based on error results, and provide the resulting intra- orinter-coded block to a residual generation unit 207 to generate residualblock data and to a reconstruction unit 212 to reconstruct the encodedblock for use as a reference picture. In some example, mode select unit203 may select a combination of intra and inter prediction (CIIP) modein which the prediction is based on an inter prediction signal and anintra prediction signal. Mode select unit 203 may also select aresolution for a motion vector (e.g., a sub-pixel or integer pixelprecision) for the block in the case of inter-prediction.

To perform inter prediction on a current video block, motion estimationunit 204 may generate motion information for the current video block bycomparing one or more reference frames from buffer 213 to the currentvideo block. Motion compensation unit 205 may determine a predictedvideo block for the current video block based on the motion informationand decoded samples of pictures from buffer 213 other than the pictureassociated with the current video block.

Motion estimation unit 204 and motion compensation unit 205 may performdifferent operations for a current video block, for example, dependingon whether the current video block is in an I slice, a P slice, or a Bslice.

In some examples, motion estimation unit 204 may perform uni-directionalprediction for the current video block, and motion estimation unit 204may search reference pictures of list 0 or list 1 for a reference videoblock for the current video block. Motion estimation unit 204 may thengenerate a reference index that indicates the reference picture in list0 or list 1 that contains the reference video block and a motion vectorthat indicates a spatial displacement between the current video blockand the reference video block. Motion estimation unit 204 may output thereference index, a prediction direction indicator, and the motion vectoras the motion information of the current video block. Motioncompensation unit 205 may generate the predicted video block of thecurrent block based on the reference video block indicated by the motioninformation of the current video block.

In other examples, motion estimation unit 204 may perform bi-directionalprediction for the current video block, motion estimation unit 204 maysearch the reference pictures in list 0 for a reference video block forthe current video block and may also search the reference pictures inlist 1 for another reference video block for the current video block.Motion estimation unit 204 may then generate reference indexes thatindicate the reference pictures in list 0 and list 1 containing thereference video blocks and motion vectors that indicate spatialdisplacements between the reference video blocks and the current videoblock. Motion estimation unit 204 may output the reference indexes andthe motion vectors of the current video block as the motion informationof the current video block. Motion compensation unit 205 may generatethe predicted video block of the current video block based on thereference video blocks indicated by the motion information of thecurrent video block.

In some examples, motion estimation unit 204 may output a full set ofmotion information for decoding processing of a decoder.

In some examples, motion estimation unit 204 may do not output a fullset of motion information for the current video. Rather, motionestimation unit 204 may signal the motion information of the currentvideo block with reference to the motion information of another videoblock. For example, motion estimation unit 204 may determine that themotion information of the current video block is sufficiently similar tothe motion information of a neighboring video block.

In one example, motion estimation unit 204 may indicate, in a syntaxstructure associated with the current video block, a value thatindicates to the video decoder 300 that the current video block has thesame motion information as the another video block.

In another example, motion estimation unit 204 may identify, in a syntaxstructure associated with the current video block, another video blockand a motion vector difference (MVD). The motion vector differenceindicates a difference between the motion vector of the current videoblock and the motion vector of the indicated video block. The videodecoder 300 may use the motion vector of the indicated video block andthe motion vector difference to determine the motion vector of thecurrent video block.

As discussed above, video encoder 200 may predictively signal the motionvector. Two examples of predictive signaling techniques that may beimplemented by video encoder 200 include advanced motion vectorprediction (AMVP) and merge mode signaling.

Intra prediction unit 206 may perform intra prediction on the currentvideo block. When intra prediction unit 206 performs intra prediction onthe current video block, intra prediction unit 206 may generateprediction data for the current video block based on decoded samples ofother video blocks in the same picture. The prediction data for thecurrent video block may include a predicted video block and varioussyntax elements.

Residual generation unit 207 may generate residual data for the currentvideo block by subtracting (e.g., indicated by the minus sign) thepredicted video block(s) of the current video block from the currentvideo block. The residual data of the current video block may includeresidual video blocks that correspond to different sample components ofthe samples in the current video block.

In other examples, there may be no residual data for the current videoblock for the current video block, for example in a skip mode, andresidual generation unit 207 may not perform the subtracting operation.

Transform processing unit 208 may generate one or more transformcoefficient video blocks for the current video block by applying one ormore transforms to a residual video block associated with the currentvideo block.

After transform processing unit 208 generates a transform coefficientvideo block associated with the current video block, quantization unit209 may quantize the transform coefficient video block associated withthe current video block based on one or more quantization parameter (QP)values associated with the current video block.

Inverse quantization unit 210 and inverse transform unit 211 may applyinverse quantization and inverse transforms to the transform coefficientvideo block, respectively, to reconstruct a residual video block fromthe transform coefficient video block. Reconstruction unit 212 may addthe reconstructed residual video block to corresponding samples from oneor more predicted video blocks generated by the prediction unit 202 toproduce a reconstructed video block associated with the current blockfor storage in the buffer 213.

After reconstruction unit 212 reconstructs the video block, loopfiltering operation may be performed reduce video blocking artifacts inthe video block.

Entropy encoding unit 214 may receive data from other functionalcomponents of the video encoder 200. When entropy encoding unit 214receives the data, entropy encoding unit 214 may perform one or moreentropy encoding operations to generate entropy encoded data and outputa bitstream that includes the entropy encoded data.

FIG. 11 is a block diagram illustrating an example of video decoder 300which may be video decoder 124 in the system 100 illustrated in FIG. 9 .

The video decoder 300 may be configured to perform any or all of thetechniques of this disclosure. In the example of FIG. 11 , the videodecoder 300 includes a plurality of functional components. Thetechniques described in this disclosure may be shared among the variouscomponents of the video decoder 300. In some examples, a processor maybe configured to perform any or all of the techniques described in thisdisclosure.

In the example of FIG. 11 , video decoder 300 includes an entropydecoding unit 301, a motion compensation unit 302, an intra predictionunit 303, an inverse quantization unit 304, an inverse transformationunit 305, and a reconstruction unit 306 and a buffer 307. Video decoder300 may, in some examples, perform a decoding pass generally reciprocalto the encoding pass described with respect to video encoder 200 (e.g.,FIG. 10 ).

Entropy decoding unit 301 may retrieve an encoded bitstream. The encodedbitstream may include entropy coded video data (e.g., encoded blocks ofvideo data). Entropy decoding unit 301 may decode the entropy codedvideo data, and from the entropy decoded video data, motion compensationunit 302 may determine motion information including motion vectors,motion vector precision, reference picture list indexes, and othermotion information. Motion compensation unit 302 may, for example,determine such information by performing the AMVP and merge mode.

Motion compensation unit 302 may produce motion compensated blocks,possibly performing interpolation based on interpolation filters.Identifiers for interpolation filters to be used with sub-pixelprecision may be included in the syntax elements.

Motion compensation unit 302 may use interpolation filters as used byvideo encoder 20 during encoding of the video block to calculateinterpolated values for sub-integer pixels of a reference block. Motioncompensation unit 302 may determine the interpolation filters used byvideo encoder 200 according to received syntax information and use theinterpolation filters to produce predictive blocks.

Motion compensation unit 302 may use some of the syntax information todetermine sizes of blocks used to encode frame(s) and/or slice(s) of theencoded video sequence, partition information that describes how eachmacroblock of a picture of the encoded video sequence is partitioned,modes indicating how each partition is encoded, one or more referenceframes (and reference frame lists) for each inter-encoded block, andother information to decode the encoded video sequence.

Intra prediction unit 303 may use intra prediction modes for examplereceived in the bitstream to form a prediction block from spatiallyadjacent blocks. Inverse quantization unit 304 inverse quantizes, i.e.,de-quantizes, the quantized video block coefficients provided in thebitstream and decoded by entropy decoding unit 301. Inverse transformunit 305 applies an inverse transform.

Reconstruction unit 306 may sum the residual blocks with thecorresponding prediction blocks generated by motion compensation unit302 or intra-prediction unit 303 to form decoded blocks. If desired, adeblocking filter may also be applied to filter the decoded blocks inorder to remove blockiness artifacts. The decoded video blocks are thenstored in buffer 307, which provides reference blocks for subsequentmotion compensation/intra prediction and also produces decoded video forpresentation on a display device.

FIG. 12 is a flowchart representation of a method for video processingin accordance with the present technology. The method 1200 includes, atoperation 1210, performing a conversion between a picture of a video anda bitstream representation of the video. The picture comprises one ormore sub-pictures, and the bitstream representation conforms to a formatrule that specifies that a length of a syntax element is equal toCeil(Log 2(SS)) bits. SS is greater than 0, and the syntax elementindicating a horizontal or a vertical position of a top-left corner of acoding tree unit of a sub-picture of the picture.

In some embodiments, the format rule further specifies that a defaultvalue of a length of a second syntax element is equal to Ceil(Log2(SS))−P, where SS is greater than 0. The second syntax elementindicating a default width or a default height of a sub-picture of thepicture. In some embodiments, a maximum picture width in luma samples isrepresented as pic_width_max_in_luma_samples and a dimension of a codingtree block is represented as CtbSizeY. SS is equal to(pic_width_max_in_luma_samples+RR)/CtbSizeY in case the syntax elementspecifies the horizontal position of the top-left corner of the codingtree unit or the default width of the sub-picture, RR being a non-zerointeger. In some embodiments, a maximum picture height in luma samplesis represented as pic_height_max_in_luma_samples and a dimension of acoding tree block is represented as CtbSizeY. SS is equal to(pic_height_max_in_luma_samples+RR)/CtbSizeY in case the syntax elementspecifies the vertical position of the top-left corner of the codingtree unit or the default height of the sub-picture, RR being a non-zerointeger. In some embodiments, RR=CtbSizeY−1.

FIG. 13 is a flowchart representation of a method for video processingin accordance with the present technology. The method 1300 includes, atoperation 1310, performing a conversion between a picture of a video anda bitstream representation of the video, wherein the picture comprisesone or more sub-pictures. The bitstream representation conforms to aformat rule that specifies that different sub-pictures have differentidentifiers.

In some embodiments, the format rule specifies that identifiers of oneor more sub-pictures are included at a video unit level, the video unitcomprising a sequence parameter set, a picture parameter set, or apicture header. In some embodiments, a first syntax flag at the sequenceparameter set indicates whether signaling of the identifiers of the oneor more sub-pictures is present at the sequence parameter set level, asecond syntax flag at the picture parameter set indicates whethersignaling of the identifiers of the one or more sub-pictures is presentat the picture parameter set level, and a third syntax flag at thepicture header indicates whether signaling of the identifiers of the oneor more sub-pictures is present at the picture header level. At leastone of the first syntax flag, the second syntax flag, or the thirdsyntax flag is equal to 1. In some embodiments, signaling of theidentifiers of the one or more sub-pictures is omitted at the pictureheader level in case the first syntax flag indicates that signaling ofthe identifiers of the one or more sub-pictures is present at thesequence parameter set level.

In some embodiments, the format rule specifies that identifiers of oneor more sub-pictures are included in a list of sub-picture identifiers.In some embodiments, the identifier of a first sub-picture in the listis denoted as SubpicIdList[i] and the identifier of a second sub-pictureis denoted as SubpicIdList[j], where j=i−P. The format rule specifiesthat a difference D[i] between SubpicIdList[i] and SubpicIdList[j] isindicated in the bitstream representation. In some embodiments, P isequal to 1. In some embodiments, i>P. In some embodiments, D[i] isgreater than 0. In some embodiments, D[i]−1 is included in the bitstreamrepresentation.

In some embodiments, the list of sub-picture identifiers is determinedbased on an order that the sequence parameter set is considered first,the picture parameter set is considered next, and the picture header isconsidered last. In some embodiments, the list of sub-pictureidentifiers is determined based on an order that the picture head isconsidered first, the picture parameter set is considered next, and thesequence parameter set is considered last.

In some embodiments, the format rule specifies that, in case identifiersof one or more sub-pictures are omitted at one or more video unitlevels, default values are assigned to the identifiers in a list ofsub-picture identifiers. The one or more video units comprise at least asequence parameter set, a picture parameter set, or a picture header. Insome embodiments, an identifier of a sub-picture in the list is denotedas SubpicIdList[i], and a default value for SubpicIdList[i] is i+P, Pbeing an offset value.

FIG. 14 is a flowchart representation of a method for video processingin accordance with the present technology. The method 1400 includes, atoperation 1410, determining, for a conversion between a block of a firstsub-picture of a video and a bitstream representation of the video,whether to apply a deblocking process across an edge between the blockand a neighboring block of a second sub-picture based on whether a loopfiltering process is allowed across subpicture boundaries. The method1400 also includes, at operation 1420, performing the conversion basedon the determining.

In some embodiments, a first syntax flag indicates whether the loopfiltering process is allowed to access samples across boundaries for thefirst side of the edge and a second syntax flag indicates whether theloop filtering process is allowed to access samples across boundariesfor the second side of the edge. The edge is not filtered in case atleast one of the first syntax flag or the second syntax flag indicatesthat the loop filtering process is disallowed. In some embodiments, thefirst syntax flag indicates that the loop filtering process is allowedto access samples across boundaries for the first side of the edge, andthe edge is not filtered due to the second syntax flag indicating thatthe loop filtering process is disallowed to access samples acrossboundaries for the second side of the edge.

In some embodiments, the first side of the edge is filtered and whetherthe second side of the edge is filtered are determined separately fromeach other. In some embodiments, samples on the first side of the edgeare filtered due to the first syntax flag being 1. In some embodiments,samples on the second side of the edge are filtered due to the secondsyntax flag being 1. In some embodiments, the first side of the edge isin the first sub-picture, and the second side of the edge is in thesecond sub-picture.

FIG. 15 is a flowchart representation of a method for video processingin accordance with the present technology. The method 1500 includes, atoperation 1510, performing a conversion between a video and a bitstreamrepresentation of the video. The bitstream representation conforms to aformat rule that specifies a syntax element indicating a maximum blocksize used for a transform skip coding tool in a picture parameter set issignaled independently from any syntax flags in a sequence parameterset.

FIG. 16 is a flowchart representation of a method for video processingin accordance with the present technology. The method 1600 includes, atoperation 1610, performing a conversion between a video and a bitstreamrepresentation of the video. The bitstream representation conforms to aformat rule that specifies a syntax element indicating a maximum blocksize used for a transform skip coding tool is signaled based on a syntaxflag in a sequence parameter set.

In some embodiments, the syntax element is included in a sequenceparameter set or a picture header. In some embodiments, the syntaxelement comprises log 2_transform_skip_max_size_minus2. In someembodiments, the syntax flag in the sequence parameter set comprisessps_transform_skip_enabled_flag.

FIG. 17 is a flowchart representation of a method for video processingin accordance with the present technology. The method 1700 includes, atoperation 1710, performing a conversion between a current block of avideo and a bitstream representation of the video. The method 1700 alsoincludes, at operation 1720, determining, after the conversion, a mannerof updating a history-based motion vector prediction table based onwhether the current block was coded using a geometry partition mode inwhich a block is predicted by a weighted sum of at least twopredictions. Weights for the weighted sum are generated for at least twopartitions. At least some partitions have an angular edge, and whereinthe history-based motion vector prediction table includes motioncandidates based on previously coded blocks of the video.

In some embodiments, the history-based motion vector prediction table isnot updated in case the current block is coded using the geometrypartition mode. In some embodiments, the history-based motion vectorprediction table is updated in case the current block is coded using thegeometry partition mode. In some embodiments, the history-based motionvector prediction table is updated using motion information of oneprediction of the current block. In some embodiments, the history-basedmotion vector prediction table is updated using motion information ofmultiple predictions of the current block.

FIG. 18 is a flowchart representation of a method for video processingin accordance with the present technology. The method 1800 includes, atoperation 1810, performing a conversion between a current processingunit of a video and a bitstream representation of the video using across-component adaptive loop filtering process in which chroma samplesare filtered based on corresponding luma samples. The current processingunit comprises an adaptive loop filtering processing unit determined bytwo virtual boundaries. Luma samples that are located outside of thecurrent processing unit are excluded for filtering chroma samples of thecurrent processing unit.

In some embodiments, the luma samples that are located outside of thecurrent processing unit are padded, and the padded luma samples are usedfor filtering the chroma samples of the current processing unit.

FIG. 19 is a flowchart representation of a method for video processingin accordance with the present technology. The method 1900 includes, atoperation 1910, performing a conversion between a current processingunit of a video and a bitstream representation of the video using across-component adaptive loop filtering process in which chroma samplesare filtered based on corresponding luma samples. The current processingunit comprises an adaptive loop filtering process unit bounded by twovirtual boundaries. Luma samples that are located outside of the currentprocessing unit are used for filtering chroma samples of the currentprocessing unit.

In some embodiments, the conversion generates the video from thebitstream representation. In some embodiments, the conversion generatesthe bitstream representation from the video.

Some embodiments of the disclosed technology include making a decisionor determination to enable a video processing tool or mode. In anexample, when the video processing tool or mode is enabled, the encoderwill use or implement the tool or mode in the processing of a block ofvideo, but may not necessarily modify the resulting bitstream based onthe usage of the tool or mode. That is, a conversion from the block ofvideo to the bitstream representation of the video will use the videoprocessing tool or mode when it is enabled based on the decision ordetermination. In another example, when the video processing tool ormode is enabled, the decoder will process the bitstream with theknowledge that the bitstream has been modified based on the videoprocessing tool or mode. That is, a conversion from the bitstreamrepresentation of the video to the block of video will be performedusing the video processing tool or mode that was enabled based on thedecision or determination.

Some embodiments of the disclosed technology include making a decisionor determination to disable a video processing tool or mode. In anexample, when the video processing tool or mode is disabled, the encoderwill not use the tool or mode in the conversion of the block of video tothe bitstream representation of the video. In another example, when thevideo processing tool or mode is disabled, the decoder will process thebitstream with the knowledge that the bitstream has not been modifiedusing the video processing tool or mode that was enabled based on thedecision or determination.

The disclosed and other solutions, examples, embodiments, modules andthe functional operations described in this document can be implementedin digital electronic circuitry, or in computer software, firmware, orhardware, including the structures disclosed in this document and theirstructural equivalents, or in combinations of one or more of them. Thedisclosed and other embodiments can be implemented as one or morecomputer program products, e.g., one or more modules of computer programinstructions encoded on a computer readable medium for execution by, orto control the operation of, data processing apparatus. The computerreadable medium can be a machine-readable storage device, amachine-readable storage substrate, a memory device, a composition ofmatter effecting a machine-readable propagated signal, or a combinationof one or more of them. The term “data processing apparatus” encompassesall apparatus, devices, and machines for processing data, including byway of example a programmable processor, a computer, or multipleprocessors or computers. The apparatus can include, in addition tohardware, code that creates an execution environment for the computerprogram in question, e.g., code that constitutes processor firmware, aprotocol stack, a database management system, an operating system, or acombination of one or more of them. A propagated signal is anartificially generated signal, e.g., a machine-generated electrical,optical, or electromagnetic signal, that is generated to encodeinformation for transmission to suitable receiver apparatus.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, and it can bedeployed in any form, including as a stand-alone program or as a module,component, subroutine, or other unit suitable for use in a computingenvironment. A computer program does not necessarily correspond to afile in a file system. A program can be stored in a portion of a filethat holds other programs or data (e.g., one or more scripts stored in amarkup language document), in a single file dedicated to the program inquestion, or in multiple coordinated files (e.g., files that store oneor more modules, sub programs, or portions of code). A computer programcan be deployed to be executed on one computer or on multiple computersthat are located at one site or distributed across multiple sites andinterconnected by a communication network.

The processes and logic flows described in this document can beperformed by one or more programmable processors executing one or morecomputer programs to perform functions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an field programmable gate array (FPGA) or anapplication specific integrated circuit (ASIC).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read only memory ora random-access memory or both. The essential elements of a computer area processor for performing instructions and one or more memory devicesfor storing instructions and data. Generally, a computer will alsoinclude, or be operatively coupled to receive data from or transfer datato, or both, one or more mass storage devices for storing data, e.g.,magnetic, magneto optical disks, or optical disks. However, a computerneed not have such devices. Computer readable media suitable for storingcomputer program instructions and data include all forms of non-volatilememory, media and memory devices, including by way of examplesemiconductor memory devices, e.g., erasable programmable read-onlymemory (EPROM), electrically erasable programmable read-only memory(EEPROM), and flash memory devices; magnetic disks, e.g., internal harddisks or removable disks; magneto optical disks; and compact disc,read-only memory (CD ROM) and digital versatile disc read-only memory(DVD-ROM) disks. The processor and the memory can be supplemented by, orincorporated in, special purpose logic circuitry.

While this patent document contains many specifics, these should not beconstrued as limitations on the scope of any subject matter or of whatmay be claimed, but rather as descriptions of features that may bespecific to particular embodiments of particular techniques. Certainfeatures that are described in this patent document in the context ofseparate embodiments can also be implemented in combination in a singleembodiment. Conversely, various features that are described in thecontext of a single embodiment can also be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. Moreover, the separation of various system components in theembodiments described in this patent document should not be understoodas requiring such separation in all embodiments.

Only a few implementations and examples are described and otherimplementations, enhancements and variations can be made based on whatis described and illustrated in this patent document.

What is claimed is:
 1. A method of video processing, comprising:determining, for a conversion between a chroma block of a currentprocessing unit of a current subpicture of a current picture of a videoand a bitstream of the video, that a cross component adaptive loopfiltering operation is applied to the chroma block, wherein the currentpicture comprises one or more subpictures; and performing the conversionbased on the determining, wherein in the cross component adaptive loopfiltering operation, a chroma sample of the chroma block is filteredbased on information of luma samples, and wherein one or more lumasamples located outside the current processing unit are excluded fromthe filtering of the chroma sample.
 2. The method of claim 1, whereinthe current processing unit is defined by an adaptive loop filteringvirtual boundary.
 3. The method of claim 1, wherein one or more lumasamples located outside an adaptive loop filtering virtual boundary areexcluded from the filtering of the chroma sample.
 4. The method of claim3, wherein one or more luma samples inside the adaptive loop filteringvirtual boundary is used to replace the one or more luma samples locatedoutside an adaptive loop filtering virtual boundary and is included inthe filtering of the chroma sample.
 5. The method of claim 1, whereinthe current picture further comprises a video block, and wherein when anedge of the video block coincides with a boundary of a subpicture in thecurrent picture and an in-loop filtering operation across the boundaryof the subpicture is disabled, a deblocking filter process is notapplied to the edge.
 6. The method of claim 5, wherein a syntax elementindicating whether the in-loop filtering operation process across theboundary of the subpicture is disabled is included in the bitstream. 7.The method of claim 1, wherein a syntax element indicating a maximumblock size used for a transform skip coding tool is conditionallyincluded in a sequence parameter set in the bitstream based on a valueof a transform skip enabled flag included in the sequence parameter setin the bitstream.
 8. The method of claim 1, wherein the current picturefurther comprises a video block, wherein a history-based motion vectorprediction table is maintained to be used for motion vector prediction,wherein when the video block is coded in a first mode, the history-basedmotion vector prediction table is refrained from being updated based onthe video block, and wherein in the first mode, a partition schemedividing the video block into two partitions is allowed, and at leastone of the two partitions is non-square and non-rectangular.
 9. Themethod of claim 1, wherein the conversion includes encoding the currentpicture into the bitstream.
 10. The method of claim 1, wherein theconversion includes decoding the current picture from the bitstream. 11.An apparatus for processing video data comprising a processor and anon-transitory memory with instructions thereon, wherein theinstructions upon execution by the processor, cause the processor to:determine, for a conversion between a chroma block of a currentprocessing unit of a current subpicture of a current picture of a videoand a bitstream of the video, that a cross component adaptive loopfiltering operation is applied to the chroma block, wherein the currentpicture comprises one or more subpictures; and perform the conversionbased on the determining, wherein in the cross component adaptive loopfiltering operation, a chroma sample of the chroma block is filteredbased on information of luma samples, and wherein one or more lumasamples located outside the current processing unit are excluded fromthe filtering of the chroma sample.
 12. The apparatus of claim 11,wherein the current processing unit is defined by an adaptive loopfiltering virtual boundary.
 13. The apparatus of claim 11, wherein oneor more luma samples located outside an adaptive loop filtering virtualboundary are excluded from the filtering of the chroma sample.
 14. Theapparatus of claim 13, wherein one or more luma samples inside theadaptive loop filtering virtual boundary is used to replace the one ormore luma samples located outside an adaptive loop filtering virtualboundary and is included in the filtering of the chroma sample.
 15. Theapparatus of claim 11, wherein the current picture further comprises avideo block, and wherein when an edge of the video block coincides witha boundary of a subpicture in the current picture and an in-loopfiltering operation across the boundary of the subpicture is disabled, adeblocking filter process is not applied to the edge.
 16. The apparatusof claim 15, wherein a syntax element indicating whether the in-loopfiltering operation process across the boundary of the subpicture isdisabled is included in the bitstream.
 17. The apparatus of claim 11,wherein a syntax element indicating a maximum block size used for atransform skip coding tool is conditionally included in a sequenceparameter set in the bitstream based on a value of a transform skipenabled flag included in the sequence parameter set in the bitstream.18. The apparatus of claim 11, wherein the current picture furthercomprises a video block, wherein a history-based motion vectorprediction table is maintained to be used for motion vector prediction,wherein when the video block is coded in a first mode, the history-basedmotion vector prediction table is refrained from being updated based onthe video block, and wherein in the first mode, a partition schemedividing the video block into two partitions is allowed, and at leastone of the two partitions is non-square and non-rectangular.
 19. Anon-transitory computer-readable storage medium storing instructionsthat cause a processor to: determine, for a conversion between a chromablock of a current processing unit of a current subpicture of a currentpicture of a video and a bitstream of the video, that a cross componentadaptive loop filtering operation is applied to the chroma block,wherein the current picture comprises one or more subpictures; andperform the conversion based on the determining, wherein in the crosscomponent adaptive loop filtering operation, a chroma sample of thechroma block is filtered based on information of luma samples, andwherein one or more luma samples located outside the current processingunit are excluded from the filtering of the chroma sample.
 20. Anon-transitory computer-readable recording medium storing a bitstream ofa video which is generated by a method performed by a video processingapparatus, wherein the method comprises: determining, for a chroma blockof a current processing unit of a current picture of a currentsubpicture of a video, that a cross component adaptive loop filteringoperation is applied to the chroma block, wherein the current picturecomprises one or more subpictures; and generating the bitstream based onthe determining, wherein in the cross component adaptive loop filteringoperation, a chroma sample of the chroma block is filtered based oninformation of luma samples, and wherein one or more luma sampleslocated outside the current processing unit are excluded from thefiltering of the chroma sample.